during that time和during which time的不同

问题描述:

during that time和during which time的不同
The American teacher wtayed with us for three weeks,during_time we exchanged views about literature and art.
A.that B.which

during that time其实与during which time是一样的,但在这里因为是定语从句,所以就是which.
如果during which time前的逗号改成句号,或者在during which time前加连词and,就可以用during that time,意思就是“在那三周时间里”.