题目内容：

We didn't know ______such a difficult problem.
A.why we should deal with B.why to deal with
C.what to do with D.what we should do with

优质解答

C 一个困难的问题应该不知道怎麽做 且句式应该是：
We didn't know __（疑问代词）+ to do__such a difficult problem.