My idea is we should go to help him out at once.A. whatB. whenC. whichD. that

问题补充：

My idea is we should go to help him out at once.

A. what

B. when

C. which

D. that

答案：

A. what

B. when

C. which

(答案→)D. that

解析：考查表语从句。从句不缺少句子成分，故用that做引导词，只起连接作用，故选D。