◎ 题干
The boy was so tired that he fell asleep ________ his mother could take off his clothes.
[     ]
A. before  
B. after
C. while  
D. when
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◎ 解析
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◎ 知识点
    根据魔方格专家分析,试题“The boy was so tired that he fell asleep ________ his mother could take off his clothes.[ ]A. beforeB. afterC. whileD. when…”主要考查了你对  【从属连词】【状语从句】  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。