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

问题补充：

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

A. is trying

B. are trying

C. will try

D. have tried

答案：

A. is trying

(答案→)B. are trying

C. will try

D. have tried

解析：考查时态和主谓一致：句意：随着学生数量的越来越多，整个中国都在努力实现他们出国学习的梦想。从句意看是现在进行时，主语是China，因为后面用their，所以这里指中国人，谓语是复数，选B。