he referred to in his article was unknown to the general reader.A. ThatB. WhatC. WhetherD

问题补充：

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

A. That

B. What

C. Whether

D. Where

答案：

A. That

(答案→)B. What

C. Whether

D. Where

解析：考查名词性从句。What引导主语从句，在从句中作宾语，选B。