Charlie be really difficult at times even though he’s a nice person in general.A. shallB.

问题补充：

Charlie be really difficult at times even though he’s a nice person in general.

A. shall

B. should

C. can

D. must

答案：

A. shall

B. should

(答案→)C. can

D. must

解析：情态动词用法can表示（理论、经验）有时会…，可能会…。尽管查理总的来说不错但是有时他会很难相处。