Question

Alec asked the policeman ________ he worked to contact him whenever there was an accident．

1. A.
   with him
2. B.
   who
3. C.
   with whom
4. D.
   whom

Answer 1

C
解析：
该句主要说明Alec asked the policeman to contact him whenever there was an accident，其中的he worked部分显然为定语从句修饰the policeman，A项没有起引导作用的词，应排除；
work with sb．指“与某人共事”，缺少介词with的B、D项应排除。该定语从句是由“介词+whom”引导的。