21. 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. 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
23. ［2012荆州模拟］In order to achieve and guarantee basic human rights, equality of opportunity is_________ .
A. favorable B. precious
C. essential D. worthwhile
