My friend has returned from the UK,She ___at Oxford for four years ,during which we communicated …

问题描述:

My friend has returned from the UK,She ___at Oxford for four years ,during which we communicated …
…with each other on the Internet.
A.studied
B.has studied
C.had studied
D.has been studing
为什么答案是A呢,求讲解

因为只是强调“过去”的事情,强调“当时”你们在那里的时候,与“今天”没有任何联系.