--Have you ever been here before? ---Wel
题型：选择题
问题：
--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
--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