The thought he might fail in the exam worried him a lot.A. whenBwhichC. thatD. what

问题补充：

The thought he might fail in the exam worried him a lot.

A. when

Bwhich

C. that

D. what

答案：

A. when

B. which

(答案→)C. that

D. what

解析： 考查同位语从句。 he might fail in the exam是The thought的同位语从句，且从句句意完整，所以选C。