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Mua vip
LQ
Lê Quỳnh Anh
9 tháng 12 2018

The launch of the first liquid-fuelled rocket in 1926 _______ by flight historians ______ as significant as the Wright Brothers' flight. 

A. has considered/ to have been 

B. was considered/ being 

C. is considered/ to be 

D. is considered/ to have been 
#Mẫu giáo
1
DH
Dương Hoàn Anh
9 tháng 12 2018

Kiến thức: Câu bị động

Giải thích:

Công thức câu bị động thì hiện tại đơn diễn tả sự thật đúng: S + am/ is/ are + Ved/ V3

be considered sth to be ….: được coi cái gì là …

Tạm dịch: Việc phóng tên lửa nhiên liệu lỏng đầu tiên vào năm 1926 được các nhà sử học về máy bay coi là quan trọng như chuyến bay của anh em nhà Wright.

Chọn C

Đúng(0)
W
Watermelon
8 tháng 8 2021
LÀM VÀ GIẢI THÍCH GIÚP EM NHÉ19. The launch of the first liquid - fueled rocket in 196.......... by flight historians........ significant as the Wright Brothers ' flight . A. has considered to have been B. was considered / being C. is considered to be D. is considered / to have been20 .  ...............Steve to help , I'm sure he would agree .  He is so kind a person .  A. Even if you asked B. If you ask C. Were you to ask D. Should you ask21. Jenny has an ....................command of...
Đọc tiếp

LÀM VÀ GIẢI THÍCH GIÚP EM NHÉ

19. The launch of the first liquid - fueled rocket in 196.......... by flight historians........ significant as the Wright Brothers ' flight . 

A. has considered to have been B. was considered / being C. is considered to be D. is considered / to have been

20 .  ...............Steve to help , I'm sure he would agree .  He is so kind a person .  A. Even if you asked B. If you ask C. Were you to ask D. Should you ask

21. Jenny has an ....................command of Japanese cuisine .

  A. intensive B. utter C. impressive D. extreme

22. The new airport has .............a lot of changes on this island . 

A. brought about B. taken to C. counted in D. turned up

23. The new secretary is really asking for trouble , ........the boss's requests like that . 

A. to ignore B. ignore C. is ignoring D. ignoring

24. The way in which we work has ..............a complete transformation in the past decade . 

A. spent  B. undertaken C. undercovered D. underdone

25. He was accused to theft , but then ..............he as the real thief confessed to the police  appeared in broad daylight

A. appeared in broad daylight B. cleared his name C. kept it up his sleeve D. caught himself red - handed

26. The government has made a big effort to tackle the two most......... important our country . 

A. society B. socialize C. sociable D. social

27. They have signed an agreement to protect the forests .......of all over the world 

A. being cut down B. that cut down C. which are cut down D. are

28. Pat , put all your toys  away ...............someone slips and falls on them . 

A. otherwise

B increase

C provided that

D. so long as
#Tiếng anh lớp 9
2
KY
Khinh Yên
8 tháng 8 2021

19. The launch of the first liquid - fueled rocket in 196.......... by flight historians........ significant as the Wright Brothers ' flight . 

A. has considered to have been B. was considered / being C. is considered to be D. is considered / to have been

20 .  ...............Steve to help , I'm sure he would agree .  He is so kind a person .  A. Even if you asked B. If you ask C. Were you to ask D. Should you ask

21. Jenny has an ....................command of Japanese cuisine .

  A. intensive B. utter C. impressive D. extreme

22. The new airport has .............a lot of changes on this island . 

A. brought about B. taken to C. counted in D. turned up

23. The new secretary is really asking for trouble , ........the boss's requests like that . 

A. to ignore B. ignore C. is ignoring D. ignoring

24. The way in which we work has ..............a complete transformation in the past decade . 

A. spent  B. undertaken C. undercovered D. underdone

25. He was accused to theft , but then ..............he as the real thief confessed to the police  appeared in broad daylight

A. appeared in broad daylight B. cleared his name C. kept it up his sleeve D. caught himself red - handed

26. The government has made a big effort to tackle the two most......... important our country . 

A. society B. socialize C. sociable D. social

27. They have signed an agreement to protect the forests .......of all over the world 

A. being cut down B. that cut down C. which are cut down D. are

28. Pat , put all your toys  away ......IN CASE.........someone slips and falls on them . 

A. otherwise

B increase

C provided that

 

D. so long as

 

Đúng(1)
DT
Đỗ Thanh Hải
CTVVIP
8 tháng 8 2021

19. The launch of the first liquid - fueled rocket in 196.......... by flight historians........ significant as the Wright Brothers ' flight . 

A. has considered to have been B. was considered / being C. is considered to be D. is considered / to have been

20 .  ...............Steve to help , I'm sure he would agree .  He is so kind a person .  A. Even if you asked B. If you ask C. Were you to ask D. Should you ask

21. Jenny has an ....................command of Japanese cuisine .

  A. intensive B. utter C. impressive D. extreme

22. The new airport has .............a lot of changes on this island . 

A. brought about B. taken to C. counted in D. turned up

23. The new secretary is really asking for trouble , ........the boss's requests like that . 

A. to ignore B. ignore C. is ignoring D. ignoring

24. The way in which we work has ..............a complete transformation in the past decade . 

A. spent  B. undertaken C. undercovered D. underdone

25. He was accused to theft , but then ..............he as the real thief confessed to the police  appeared in broad daylight

A. appeared in broad daylight B. cleared his name C. kept it up his sleeve D. caught himself red - handed

26. The government has made a big effort to tackle the two most......... important our country . 

A. society B. socialize C. sociable D. social

27. They have signed an agreement to protect the forests .......of all over the world 

A. being cut down B. that cut down C. which are cut down D. are

28. Pat , put all your toys  away ...............someone slips and falls on them . 

A. otherwise

B in case

C provided that

D. so long as

Đúng(0)
AN
An Nhiên
27 tháng 8 2020
Choose the best answer to complete each of the following sentences. 1.He_______ playing with his dog. A.is loving B. loves C.was loving D. love 2. Oil___________ if you pour it on water. A.floated B. floats C. will be floated D. float 3. Water________at 100 degrees Celsius. A. boils B.boiling C. is boiling D. boil 4.The launch of the first liquid-fuelled rocket in 1926____________ by flight historians_______as significant as the Wright Brother's flight. A. has considered - having...
Đọc tiếp

Choose the best answer to complete each of the following sentences.

1.He_______ playing with his dog.

A.is loving B. loves C.was loving D. love

2. Oil___________ if you pour it on water.

A.floated B. floats C. will be floated D. float

3. Water________at 100 degrees Celsius.

A. boils B.boiling C. is boiling D. boil

4.The launch of the first liquid-fuelled rocket in 1926____________ by flight historians_______as significant as the Wright Brother's flight.

A. has considered - having been B. was considered - being

C. is considered - to be D. has been considered - has been

5.I'm afraid John will get drunk at the party no matter what his wife________ to prevent it.

A.would do B. were doing C.does D. will do

6."Any news from Vicky?" " Yes, She _____ tomorrow on the 9: 15 train."

A. arrives B. will have arrived C. arriving D. will have been arriving

7."Do you know it's Barb's birthday today?" " Yes, she_________a party tonight."

A. has B. is to have C. is having D. will have

8.Tom_______things roud the house, which is annoying.

A. always leaves B. has always left C. is leaving D. is always leaving

9.Teenagers________ photos of pop stars on their bedroom walls.

A. are often sticking B.often stick C. will often stick D. have often stuck

10. At least half of the world's population________more than one language

A. speak B. speaks C. have spoken D. is speaking

11. "Did you have a good time at the Browns?" "Not really. I_______I'll ever visit them again."

A. won't be thinking B. am not thinking C. have been accused - used D. are being accused - being used

12. Today, universities________of conducting "cruel and unnecessary" tests on animals,_________banned drugs such as amphetamines.

A. are accused - using B. have accoused - to use

C. have been accused - used D. are being accused - being used

13. "George is in hospital." "Yes, I've heard he_______good progress."

A. makes B. will make C.is making D.would make

14. My neighbor really gets on my nerves. She_______ the washing machine on late at night.

A. has always put B. had always put C. has always been putting D. is always putting

15. The word "Olympic"______from Olympian in Greece

A. has come B. came C.comes D. is coming

16. Three swimmers, Paul, Ed and Jim, now_______in the competition for medals.

A. is B. has been C. had been D. are

17. "Could I have a word with you, please?" " Sorry, I'm in a big hurry. My train_______in 15 minutes."

A. is leaving B. left C. has left D. will leave

18. I______ an important phone call from America. Could you tell me when it comes?

A. had expected B. have been expected C. expected D. am expecting

19. The existence of many stars in the sky________us to suspect that there may be life on another planet.

A. lead B. leading C. have led D. leads

20.______________I insist on a full refund.

A. Whatever he will say B.Whatever he said

C. Whatever he says D. Whatever he would say
#Tiếng anh lớp 10
0
LQ
Lê Quỳnh Anh
31 tháng 7 2018
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42. HISTORY OF THE HELICOPTER Although first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a...
Đọc tiếp

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.

HISTORY OF THE HELICOPTER

Although first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a prototype for the machine that we now know as the helicopter.

Early in the twentieth century, a great deal of experimentation and revision was taking place with regard to helicopter flight. The well-known phrase “two steps forward and one step back” provided an apt descriptor for early flight development. Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.

On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance. Several models followed without significance until in 1924 when another French pioneer, Etienne Oehmichen, became the first to fly a helicopter for one kilometer. It was a historic flight of 7 minutes and 40 seconds. By 1936, solutions have been found to many of the problems with helicopter flight.

With the introduction of the German Focke-Wulf Fw 61, the first practical helicopter became a reality.

Why was Paul Cornu’s flight important?

A. It was the first practical helicopter flight.

B. It lasted 7 minutes and 40 seconds.

C. It was the first time a helicopter lifted into the air without ground assistance.

D. It was the first time a helicopter lifted into the air.
#Mẫu giáo
1
DH
Dương Hoàn Anh
31 tháng 7 2018

Đáp án C


Đáp án nằm ở dòng 1 + 2 đoạn 3: “On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance”

Đúng(0)
LQ
Lê Quỳnh Anh
14 tháng 12 2017
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.HISTORY OF THE HELICOPTERAlthough first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a...
Đọc tiếp

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.

HISTORY OF THE HELICOPTER

Although first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a prototype for the machine that we now know as the helicopter.

Early in the twentieth century, a great deal of experimentation and revision was taking place with regard to helicopter flight. The well-known phrase “two steps forward and one step back” provided an apt descriptor for early flight development. Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.

On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance. Several models followed without significance until in 1924 when another French pioneer, Etienne Oehmichen, became the first to fly a helicopter for one kilometer. It was a historic flight of 7 minutes and 40 seconds. By 1936, solutions have been found to many of the problems with helicopter flight.

With the introduction of the German Focke-Wulf Fw 61, the first practical helicopter became a reality.

 

Why was Paul Cornu’s flight important?

A. It was the first practical helicopter flight

B. It lasted 7 minutes and 40 seconds

C. It was the first time a helicopter lifted into the air without ground assistance

D. It was the first time a helicopter lifted into the air
#Mẫu giáo
1
DH
Dương Hoàn Anh
14 tháng 12 2017

Đáp án C

Đáp án nằm ở dòng 1 + 2 đoạn 3: “On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance”

Đúng(0)
DM
Dương Minh
4 tháng 11 2019
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.HISTORY OF THE HELICOPTERAlthough first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a...
Đọc tiếp

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.

HISTORY OF THE HELICOPTER

Although first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a prototype for the machine that we now know as the helicopter.

Early in the twentieth century, a great deal of experimentation and revision was taking place with regard to helicopter flight. The well-known phrase “two steps forward and one step back” provided an apt descriptor for early flight development. Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.

On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance. Several models followed without significance until in 1924 when another French pioneer, Etienne Oehmichen, became the first to fly a helicopter for one kilometer. It was a historic flight of 7 minutes and 40 seconds. By 1936, solutions have been found to many of the problems with helicopter flight.

With the introduction of the German Focke-Wulf Fw 61, the first practical helicopter became a reality.

Why was Paul Cornu’s flight important?

A. It was the first practical helicopter flight.

B. It lasted 7 minutes and 40 seconds.

C. It was the first time a helicopter lifted into the air without ground assistance.

D. It was the first time a helicopter lifted into the air.
#Mẫu giáo
1
NH
Nguyen Hoang Hai
4 tháng 11 2019

Đáp án C

Đáp án nằm ở dòng 1 + 2 đoạn 3: “On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance”

Đúng(0)
DM
Dương Minh
8 tháng 4 2019
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.HISTORY OF THE HELICOPTERAlthough first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a...
Đọc tiếp

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.

HISTORY OF THE HELICOPTER

Although first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a prototype for the machine that we now know as the helicopter.

Early in the twentieth century, a great deal of experimentation and revision was taking place with regard to helicopter flight. The well-known phrase “two steps forward and one step back” provided an apt descriptor for early flight development. Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.

On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance. Several models followed without significance until in 1924 when another French pioneer, Etienne Oehmichen, became the first to fly a helicopter for one kilometer. It was a historic flight of 7 minutes and 40 seconds. By 1936, solutions have been found to many of the problems with helicopter flight.

With the introduction of the German Focke-Wulf Fw 61, the first practical helicopter became a reality.

Why was “dissymmetry” important to the early pioneers of helicopter flight?

A. It was an effect that caused helicopter to crash.

B. It equalized lift on each side of the central shaft.

C. It allowed helicopters to lift from the ground.

D. It allowed the rotor blade angles to be altered.
#Mẫu giáo
1
NH
Nguyen Hoang Hai
8 tháng 4 2019

Đáp án A

Tại sao “tính không đối xứng” lại quan trọng với những chiếc máy bay trực thăng trước đây
Đáp án nằm ở dòng 3, 4 và 5 đoạn 2: “Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.”

Đúng(0)
LQ
Lê Quỳnh Anh
7 tháng 6 2018
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.HISTORY OF THE HELICOPTERAlthough first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a...
Đọc tiếp

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.

HISTORY OF THE HELICOPTER

Although first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a prototype for the machine that we now know as the helicopter.

Early in the twentieth century, a great deal of experimentation and revision was taking place with regard to helicopter flight. The well-known phrase “two steps forward and one step back” provided an apt descriptor for early flight development. Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.

On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance. Several models followed without significance until in 1924 when another French pioneer, Etienne Oehmichen, became the first to fly a helicopter for one kilometer. It was a historic flight of 7 minutes and 40 seconds. By 1936, solutions have been found to many of the problems with helicopter flight.

With the introduction of the German Focke-Wulf Fw 61, the first practical helicopter became a reality.

 

Why was “dissymmetry” important to the early pioneers of helicopter flight?

A. It was an effect that caused helicopter to crash

B. It equalized lift on each side of the central shaft

C. It allowed helicopters to lift from the ground

D. It allowed the rotor blade angles to be altered
#Mẫu giáo
1
DH
Dương Hoàn Anh
7 tháng 6 2018

Đáp án A

Tại sao “tính không đối xứng” lại quan trọng với những chiếc máy bay trực thăng trước đây
Đáp án nằm ở dòng 3, 4 và 5 đoạn 2: “Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.”

Đúng(0)
LQ
Lê Quỳnh Anh
16 tháng 7 2019
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42. HISTORY OF THE HELICOPTER Although first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a...
Đọc tiếp

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.

HISTORY OF THE HELICOPTER

Although first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a prototype for the machine that we now know as the helicopter.

Early in the twentieth century, a great deal of experimentation and revision was taking place with regard to helicopter flight. The well-known phrase “two steps forward and one step back” provided an apt descriptor for early flight development. Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.

On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance. Several models followed without significance until in 1924 when another French pioneer, Etienne Oehmichen, became the first to fly a helicopter for one kilometer. It was a historic flight of 7 minutes and 40 seconds. By 1936, solutions have been found to many of the problems with helicopter flight.

With the introduction of the German Focke-Wulf Fw 61, the first practical helicopter became a reality.

Why was “dissymmetry” important to the early pioneers of helicopter flight?

A. It was an effect that caused helicopter to crash.

B. It equalized lift on each side of the central shaft.

C. It allowed helicopters to lift from the ground.

D. It allowed the rotor blade angles to be altered.
#Mẫu giáo
1
DH
Dương Hoàn Anh
16 tháng 7 2019

Đáp án A

Tại sao “tính không đối xứng” lại quan trọng với những chiếc máy bay trực thăng trước đây
Đáp án nằm ở dòng 3, 4 và 5 đoạn 2: “Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.”

Đúng(0)
LQ
Lê Quỳnh Anh
14 tháng 9 2018
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.HISTORY OF THE HELICOPTERAlthough first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a...
Đọc tiếp

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.

HISTORY OF THE HELICOPTER

Although first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a prototype for the machine that we now know as the helicopter.

Early in the twentieth century, a great deal of experimentation and revision was taking place with regard to helicopter flight. The well-known phrase “two steps forward and one step back” provided an apt descriptor for early flight development. Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.

On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance. Several models followed without significance until in 1924 when another French pioneer, Etienne Oehmichen, became the first to fly a helicopter for one kilometer. It was a historic flight of 7 minutes and 40 seconds. By 1936, solutions have been found to many of the problems with helicopter flight.

With the introduction of the German Focke-Wulf Fw 61, the first practical helicopter became a reality.

 

The word “envisioned” in paragraph 1 is closet in meaning to _____.

A. imagined 

B. perfected 

C. experienced 

D. taught
#Mẫu giáo
1
DH
Dương Hoàn Anh
14 tháng 9 2018

Đáp án A

Envisioned ≈ imagined: mường tượng, hình dung

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