题目内容：

-A number of college students_______ to work in China's rural  (农村的)  areas.

-Yes, we call them "college-graduate village officials". Their number is getting_______.

They brought new ideas to the less-developed villages.

A. have been encouraged; bigger and bigger

B. has been encouraged; bigger and bigger

C. have encouraged; more and more

D. has encouraging; more and more