单选题 They ______ to have done such silly things.
A. had ought B. hadn't ought
C. didn't ought D. ought not

【正确答案】 D
【答案解析】[解析] 考查情态动词的用法。根据句意；他们本不应该做这么蠢的事。 ought to 否定应为ought not to 。故本答案为[D]。