The only thing we should do now is try our best to prepare for the Academic proficiency t

问题补充：

The only thing we should do now is try our best to prepare for the Academic proficiency test.

A. what

B. that

C. all

D. which

答案：

A. what

(答案→)B. that

C. all

D. which

解析：考查定语从句关系词的选择。 定语从句修饰的先行词thing前面有the only修饰，后面的关系词只能选择that.