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：
該句主要說明Alec asked the policeman to contact him whenever there was an accident，其中的he worked部分顯然為定語從句修飾the policeman，A項沒有起引導作用的詞，應排除；
work with sb．指“與某人共事”，缺少介詞with的B、D項應排除。該定語從句是由“介詞+whom”引導的。