Great changes ___ in the city, and a lot of factories ___.

A．have been taken place, have been set up

B．have taken place, have been set up

C．have taken place, have set up

D．were taken place, were set up

感受器有哪些共同生理特征（）

A.需适宜刺激

B.有感觉阈值

C.容易疲劳

D.有适应现象

E.有换能作用