单选题 The atmosphere ______ certain gases mixed together in definite proportion.

A、 consists of
B、 consists in
C、 insists on
D、 persists in

【正确答案】 A

【答案解析】[分析] 本题考查动词短语辨析。选择中，consist of=be made up of或be composed of由…组成；consist in=lie in在于；insist on=persist in：坚持，执意。本句的意思为：“大气层由多种气体混合组成，它们各占一定比率”。故A符合题意。