-You have given them some advice.-- So I did but who cared what I said?A. mustB.

问题补充：

---- You have given them some advice.

---- So I did, but who cared what I said?

A. must

B. ought to

C. might

D. could

答案：

A. must

(答案→)B. ought to

C. might

D. could

解析：考查情态动词。ought to have done 本该做某事而实际上没有做，句意：你本该给他们提一些建议的。我的确该给他们提一些建议，但是谁在乎我说的话呢？所以选B。