21. ［2012吉安模拟］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
22. ［2012延吉模拟］The leader of the factory told us that very little ________ was made of the waste material in the past.
A. cost B. value C. use D. matter
