Mark the letter A, B, C, or D on your answer sheet to indicate the word that is OPPOSITE in meaning to the underlinedpart in each of the following questions
Certain courses are compulsory; others are optional
A. voluntary
B. pressure
C. mandatory
D. free
Đáp án : C
Optional = tùy chọn, voluntary = tình nguyện, pressure= áp lực, mandatory= bắt buộc, free= tự do