Scientists are working hard to make possible for people to live on Mars in the future.A.

问题补充：

Scientists are working hard to make possible for people to live on Mars in the future.

A. it

B. that

C. this

D. one

答案：

(答案→)A. it

B. that

C. this

D. one

解析：句意：科学家们正在努力工作，使将来人们在火星上生活成为可能。考查句型：make it adj to do sth,故选A。

考点: 考查代词的用法。