If they had studied hard, they could do it easily now 这个虚拟语气中

题目

If they had studied hard, they could do it easily now 这个虚拟语气中
这个虚拟语气中,虚拟语气是与过去事实相反,从句用had+过去分词,那么主句不是应该用should/would/could/might+have过去分词的吗? 为什么这个句子中的主句用现在时啊.虽然我知道主句与从句的时态要不一致

答案

由于所述事情是现在发生的,now,所以动词用现在时do.如果是过去发生的事情,就用have done,如：
If they had studied hard,they could have done it easily.