◎ 题干
— 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
◎ 答案
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“—I wonder how much you charge for your services.— The first two are free _____the third costs $30. [ ]A. whileB. until C. when D. before …”主要考查了你对  【从属连词】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。