Question

______ he referred to in his article was unknown to the general reader.

  A. That            B. What              C. Whether               D. Where

Answer 1

A

解析:

主要测试主语从句。句子______ he referred to in his article在复合句中充当主语，同时该句子中缺少介词to的宾语，双重作用。答案一目了然。