I have been here for three years.=It is three years ______I____here

问题描述:

I have been here for three years.=It is three years ______I____here

It is three years since I have been here.

I have been here for three years.=It is three years since I came here

I have been here for three years.=It is three years since I came here
It is +时间+since+从句 是万能公式

since came

I have been here for three years.=It is three years since I came here.
It is +时间+since从句,相当于现在完成时