The amounts of oxygen and nitrogen in the air almost always remain stable, but the amount of water vapor vary considerably.
A. The amounts
B. almost always
C. amount of
D. vary
the amount of + N(không đếm được) => V (số ít)
vary => varies
=> The amounts of oxygen and nitrogen in the air almost always remain stable, but the amount of water vapor varies considerably.
Tạm dịch: Lượng oxy và nitơ trong không khí hầu như vẫn luôn ổn định, nhưng lượng hơi nước thì thay đổi đáng kể.
Đáp án: D
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