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,十分感谢。。
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
不知道应该怎样