Although he had made many mistakes in his composition,____ have laughed at him?

题目

Although he had made many mistakes in his composition,____ have laughed at him?
A.Oughtn't we B.Should we C.Oughtn't to we D.Ought to we
答案应该选B,为什么?请说明原因,

答案

反义疑问句 语义上AC都错
ought to do没疑问的说法吧..