— Why do you do volunteer work in the North-West?— I to improve the lives of the children

问题补充：

— Why do you do volunteer work in the North-West?

— I to improve the lives of the children there through my efforts．

A. was trying

B. have tried

C. am trying

D. tried

答案：

A. was trying

B. have tried

(答案→)C. am trying

D. tried

解析：句意：--你为什么在西北做志愿者的工作？--我在努力通过自己的努力改善那里孩子的生活。从第一句话：Why do you do volunteer work in the North-West?可知是现在正在做，用现在进行时，选C。