Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) CLOSEST in meaning to the
underlined word(s) in each of the following questions.
Oil is one of the principal sources of energy.
A. most important
B. most difficult
C. most popular
D. most expensive
Đáp án A
Giải thích: principal ≈ most important
Tạm dịch: Dầu thô là một trong những nguồn năng lượng quan trọng