(2012·浙江高考)Had they known what was ing next, they second thoughts.
A. may have
B. could have
C. must have had
D. might have had
网友回答
A. may have
B. could have
C. must have had
(答案→)D. might have had
解析：选D 根据“Had they known ...”可知，此处是省略了if的条件句，表示与过去事实相反的假设，所以主句用should/would/could/might＋have done结构，故D项正确。