23. Tom had to be told two or three times he could remember what the teacher said.A. befo

问题补充：

23. Tom had to be told two or three times he could remember what the teacher said.

A. before

B. when

C. until

D. As

答案：

(答案→)A. before

B. when

C. until

D. As

解析：

23．A(解析：考查连词。before 到……为止；在……之前when“当……时候until直到……为止”as“当……时候”，until强调动作的延续性，其中tell并非延续性动词，另根据句意“老师说两三遍之后汤姆才能记住。”因此选A。)