Great changes in the small city in the last 20 years.
A. have taken place
B. took place
C. had taken place
D. are happening
网友回答
(答案→)A. have taken place
B. took place
C. had taken place
D. are happening
解析：考查时态：时间是in the last 20 years，和现在完成时连用，句意是：在过去的20年里，这个小镇已经发生了巨大的改变。选A。