The reform has changed the whole nation. It cannot remain it used to be.A. what B. whereC

问题补充：

The reform has changed the whole nation. It cannot remain it used to be.

A. what

B. where

C. which

D. when

答案：

(答案→)A. what

B. where

C. which

D. when

解析：A 考察表语从句。此处remain是一个联系动词，其后选用what引导一个表语从句，同时what在从句中作为be的表语。