问题
选择题
The boy was so tired that he fell asleep _______ his mother could take off his clothes.
A．before
B．after
C．while
D．when
答案
答案：A
题目分析：句意：这个男孩太累了，以至于在他的妈妈给他脱衣服之前，他就睡着了。Before在……之前 after在 …… 之后 while然而 when当…… 时候，选A。