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Câu hỏi: Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.
(A) The amounts of oxygen and nitrogen in the air (B) almost always remain (C) stable, but the amount of water vapor (D) vary considerably.
A. The amounts of
B. almost always
C. stable
D. vary
(A) The amounts of oxygen and nitrogen in the air (B) almost always remain (C) stable, but the amount of water vapor (D) vary considerably.
A. The amounts of
B. almost always
C. stable
D. vary
- The amount of + N + V chia số ít: số lượng ....
Do đó: vary => varies
Do đó: vary => varies
Đáp án D.