I suppose they have known about it ,(

题目

I suppose they have known about it ,(
A.am I B.am not I C.have they D.haven't they

答案

D
反义疑问句,当主语有think suppose等词,表示想法、看法,后面的分句应该以该词引导的宾语从句的主语一致
所以后面应该用they ,时态是现在完成时,即 haven't they