Question

Great changes have taken place in the last few years.在过去几年里不

Answer 1

是过去完成时.句子说的那些事情已经发生,如果有些（其他）事情还在发生,句子可以这样说：

Great changes have taken place,and are still taking place,in the last few years.

可以用 happen 代替,比如：

Great changes have happened in the last few years.

也可以用 occurred

但 taken place 比较雅致.