How time flies!Three years _since i became a middle school student.

问题描述:

How time flies!Three years _since i became a middle school student.
A、has passed B、have passed C、passed D、passes

A,因为后面有since,所以是从过去到现在.用完成时,然后three years 就是个时间,后面has用单数形式就行了