Question

since引导的时间状语从句可以用否定吗

Answer 1

可以

首先,since表示"自从.以来",表示的动作是从过去以来一直持续到现在,所以since引导的从句要用一般过去时态,但主句只能用现在完成时态,因为现在完成时态表示的动作就是从过去一直持续到现在.如以下句子.

I have taught English since 1999.

I have lived here since I worked here.

He has been here since he joined the army;