请问：I didn't know it were you.为什么一定要用were呢?

请问：I didn't know it were you.为什么一定要用were呢?
请问：I didn't know it were you.为什么一定要用were呢?

请问：I didn't know it were you.为什么一定要用were呢?
语法,记住就好了.意思是原来不知道（didnt know就是过去不知道）,但是说这句话的时候知道了.所以用过去时.或者理解过虚拟语气.

虚拟语气。

因为说这句话的时候说话人已经知道是：“你”，你看前面的时态是过去时，说的就是过去他不知道是“你”，所以这里含有虚拟的语气，要用were。