Hóa hơi 4,6g chất A thì thu được khí B biết \(d_{B/He}\)=11,5 .Biết trong A, C chiếm 52,174% về khối lượng ,H chiếm 13,043% về khối lượng ,còn lại là oxi

a,Tính thể tích của B ở đktc

b,Tìm công thức của A

c,Tính số mol mỗi nguyên tố có trong 6,9g A

Read the passage about some future predictions and answer the questions.
Circle A, B, C or D. (1,0 pt)
Dr Pearson, a futurologist believes in 2045 buildings will be made from concrete
plastics and shape-changing materials that can heal themselves and the builders will have
super-strength skeletons creating half-man, half-machine workers. There will be a need for
new kinds of elevators using magnetic systems. 
By mid-century, buildings will be miles tall and some may be so large that their
capacity enables them to function as small cities in their own right. As these buildings rise
through the clouds, windows will be replaced by reality virtual screens so people can
choose any view they like. However, lack of exposure to pathogens will cause more
allergies. Due to health concerns, scents, candles, incense are also likely to be more strongly
regulated, added Dr Pearson. 
28. When does Dr Pearson make these predictions?
  A. now B. in 2045 C. after 2045 D. before 2045
29. What can future buildings do?
    A. change shapes B. use machines C. self-heal D. create machines
30. What is TRUE about future buildings?
  A. They will be very big. B. They will be very tall.
  C. They will be very modern. D. They will be very old
31. What will cause more allergies?
    A. incense B. pathogens C. candles D. allergies
32. A futurologist is someone who _____________ the future.
    A. believes in B. predicts C. adds to D. builds

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Rewrite the following sentences, stay the same meaning of the first sentences.
(1,0pt)
33. People will decorate their houses to welcome New Year.
Their houses……………………………………………………………..………………
34. The distance between my house and school is about 2 kms
It’s ………………………………………………………………………………………
35. These are her shoes. (hers)
 These……………………………………………………………………………………
36. My brother often stayed up late to watch TV when he was fifteen. (used )
 My brother used………………………………………………………………….…….…
37. Be careful or you’ll fall off your bicycle. (If)
If …………………………………………………………………………………………..

h2o+co2= ???