7. —Does Liu Hui serve in the army?
问题描述：
7. —Does Liu Hui serve in the army?
—No, but he in the army for three years.
A. servedB. has served
C. is servingD. would serve
用过去完成时 是一般过去式?
答
A.served
这里面只能选A,sever是个延续性动词,后面可以跟一段时间
按理说也可以用过去完成时的,但选项里没有