In the United States there is always flow of people to areas of country where more jobs

问题补充：

In the United States, there is always flow of people to areas of country where more jobs can be found.

A. a; the

B. the ; a

C. the; the

D. a; a

答案：

(答案→)A. a; the

B. the ; a

C. the; the

D. a; a

解析：一群人流，a flow of 固定搭配；特指能找到工作的那个地方，所以用定冠词。