If my father were here he would be very happy，----？为什么用wouldn't he

If my father were here he would be very happy，----？为什么用wouldn't he

（1）If my father were here he would be very happy，wouldn't he？译文：要是我爸爸在这儿的话，他一定会很开心。不是吗？
（2）前半部分是一个复合句，前面是if引导的条件状语从句，If my father were here 。后面是主句he would be very happy。最后是反意疑问句，wouldn't he？反意疑问句的谓语要与前面主句的谓语动词一致，并用其否定形式。
（3）这一句话是虚拟语气，表示与目前的事实相反的假设。其实我的父亲不在这儿。所以从句用过去式，不能用was，只能用were.这是约定俗成的，没有道理可讲。主句是would+动词原形。
希望对你有所帮助。
祝你进步。