--Dose Liu Hui serve in the army?
问题描述：
--Dose Liu Hui serve in the army?
--No,but he ( ) in the army for three years.
A served B has served C is aerving D would serve
答
选A
--Dose Liu Hui serve in the army?
既然回答的是NO,说明他现在已经不在部队了,不可能用现在完成时,因为现在完成时表示持续到现在的意思,应选A