英语虚拟语气选择题应该怎么选择时态

题目

英语虚拟语气选择题应该怎么选择时态
i can't stand him.he always talks as though he __everything
A knew B knows C has known D had known
总是区分不开什么时候应该用过去时什么时候应该用过去完成是,求详解,.
i would have told him the answer had it been possible but i __so busy then。
A had been
B were
C was
Dwould be

答案

选A as though这个短语是好像得意思 他实际不知道 后半句是虚拟 前半句是一般现在的事实 所以选过去时
补充 选C 前半句是虚拟语气 对过去的虚拟 后半句说的是过去的事实 该用什么时态用什么时态
过去完成时表示过去的过去
对过去的虚拟用过去完成时
对现在的虚拟用过去时