问题
选择题
(2012·浙江高考)Had they known what was coming next, they ________ second thoughts.
A．may have
B．could have
C．must have had
D．might have had
答案
答案：D
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。