SINCE用在现在完成时句子时,现在完成时的动词要用延续行为动词,SINCE后跟过去时句子.这里说的过去时是指一般过去时一种吗?It's three years since he has worked there.和
It's three years since he worked there.第二句对吗?since不是只用于完成时吗?