---Hi. Lucy! What’s wrong with you? You look so worried.---I have many problems to solve

问题补充：

---Hi. Lucy! What’s wrong with you? You look so worried.

---I have many problems to solve, but I don’t know first.

A. how to deal with

B. when to deal with

C. what to deal with

D. how to do with

答案：

A. how to deal with

B. when to deal with

(答案→)C. what to deal with

D. how to do with

解析：deal with处理，不定式短语中缺少逻辑宾语，故选C，做什么。How和when不能做宾语，只能做状语。