是否考察虚拟语气请写出判断依据

1.答案：C.
2.翻译：如果我（当时）知道他不能来的话,我本不会给他送去邀请信的.
3.
1）此题的确考查虚拟语气.
if引导的条件状语从句,如果是对过去所发生动作的虚拟,则if从句使用过去完成时,而主句使用“would have done sth”结构.
2）该题还采用了虚拟语气中的倒装语法.该语法规定如下：如果If从句含有had/were/should,则可以将其提前至从句句首,并省略if.
即：Had I known that he wasn't able to come,I wouldn't have sent him the invitation letter.
= If I had known that he wasn't able to come,I wouldn't have sent him the invitation letter.
3）判断依据：该题主句中的wouldn't have sent...和倒装的Had I known都表明该句采用了虚拟语气.