题目：
I _____able to tell you everything you want to know, if l _____what happened to him last night.
(A) were / knew
(B) were / had known
(C) would be / had known
(D) would be / knew
疑问：答案是c
想问为什么d不行呢？不是与现在事实相反的假设吗？谢谢～～