1.if he___ here this afternoon i would go with him.a.should be b.were 答案是b为什么不能选a?a也是对将来的虚拟啊

would是will的过去时，所以前面也要用过去时

a也是对将来的虚拟，但should be/do是主句中的谓语动词形式。横线处是if条件从句的谓语动词形式，要求用一般过去时的were/did.

if引导的条件状语从句,虚拟语气的,有以下几种情况：
1、if were to do,would do
2、if +过去式,would have done
3、if had done,should have done