--Have you ever been here before? ---Well, I once here for four years. Those days are rea

--Have you ever been here before?
---Well, I once here for four years. Those days are really unforgettable.
A. have stayed
B. had stayed
C. have been staying
D. stayed

A. have stayedB. had stayedC. have been staying(答案→)D. stayed解析：考查时态。根据语境及时间状语for four years可知，用一般过去时。句意：——你以前来过这里么？——嗯，我在这里呆过四年，那些岁月真的难忘。

好好学习下