The scientists are studying the effects of human activitiesthe environment.A. inB. atC. on

问题补充：

The scientists are studying the effects of human activitiesthe environment.

A. in

B. at

C. on

D. with

答案：

A. in

B. at

(答案→)C. on

D. with

解析：此处所填的介词与effects搭配, 对……的有影响, 用 effect on/upon表示。我们也可以联想所学短语 have an effect on sth。