---What the forest of Yangzhou in the last 30 years?
---Yangzhou has bee much greener.
A. has happened to
B. was happened to
C. has happened at
D. is happening
网友回答
(答案→)A. has happened to
B. was happened to
C. has happened at
D. is happening
解析：句意：在过去三十年当中，扬州的森林发生了什么？——扬州变得更加绿色了。短语happen to……发生了什么事。结合语境可知上文描述的是从过去一直持续到现在的动作，故用现在完成时态，选A。