The most important thing we should think about is we should do next.A. what; that B. tha

问题补充：

The most important thing we should think about is we should do next.

A. what; that

B. that;that

C. that;what

D. which;what

答案：

A. what; that

B. that;that

(答案→)C. that;what

D. which;what

解析：句意：我们应该考虑的最重要的事情就是接下来我们应该做什么。结合语境可知前文是定语从句，先行词thing前有限定性修饰词The most important，故指物的引导词只能用that。下文是宾语从句，缺少逻辑宾语，故引导词用what，选C。