but i don't think you can smoke here.I didn't know this is a...

问题描述:

but i don't think you can smoke here.I didn't know this is a...
为什么是didn't

用did not因为回答者所要表述的是他之前不知道不能抽烟这一个事实.表述的是过去的状态所以使用did not,望采纳