An increasing number of students year by year across China hard to realize their dream of

问题补充：

An increasing number of students,year by year,across China hard to realize their dream of studying abroad.

A. try

B. have tried

C. will try

D. are trying

答案：

A. try

B. have tried

C. will try

(答案→)D. are trying

解析：考查动词时态。根据语境可知是很长时间内一直在重复进行的动作。