如题所述
It is some time(一段时间) + since引导的时间状语从句。
时态的话,采用一般过去时。
例:
It is five years since I left here.
我离开这里有五年了.
(2)附加说明,如果is改为was,那后面是完成时态
It was +一段时间+ since+过去完成时
It was ten years since I had enjoyed a good drink.