---- I wonder how much you charge for your services.---- The first two are free
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---- I wonder how much you charge for your services.
---- The first two are free ____ the third costs $30.
A.while
B.until
C.when
D.Before
试题答案
A
考查连词的用法。这里起转折作用,while表示“但是”,可接句子.“前两个免费,但第三个要收费30元”