they had to finish the work before they went home yesterday,didn't they?为什么不能用hadn't they
问题描述：
they had to finish the work before they went home yesterday,didn't they?为什么不能用hadn't they
答
yesterday 一般过去时标志
答
应为主句用的的一般过去时，要保持一致的时态
答
因为had在这里是实义动词,不是助动词