There____great changes in our country since 1979A have been B were Chas been D are?选哪个?

There____great changes in our country since 1979A have been B were Chas been D are?选哪个?
There____great changes in our country since 1979
A have been B were Chas been D are?选哪个?

There____great changes in our country since 1979A have been B were Chas been D are?选哪个?
选 A have been
因为后面的时间词 since 1979,表示的是从1979年以来,所以用完成时.
而主语 great changes 是复数,所以用 have been.