If I()that you were busy last night,I wouldn't have called.

问题描述:

If I()that you were busy last night,I wouldn't have called.
A.knew B.know C.have known D.had known

D.Had known
虚拟语气,如表示于过去事实相反的假设.
句型:条件从句 主句
过去完成时 should(would) have+ 过去分词