21. Attracting  ______ senior citizens, Florida is ______ home to the largest population of elder Americans.   

A. /, /            B. the, the            C. the, /              D. /, a

22. ______ of the land in my hometown ______ covered with trees and grass.

   A. Two third; is     B. Two third; are      C. Two thirds; is       D. Two thirds; are

23.Although the Roma couldn’t be forced to pay taxes, they couldn’t vote ______ they agreed to _____the government.

   A. unless; submit to  B. until; correspond to C. when; resign to   D. while; compromise to