The problem this material can be used in our factory has been solved.A. thatB. whatC. whe

问题补充：

The problem this material can be used in our factory has been solved.

A. that

B. what

C. whether

D. why

答案：

(答案→)A. that

B. what

C. whether

D. why

解析：考查同位语从句。That引导的同位语从句That this material can be used in our factory说明The problem的内容。