21.It is said that books on ______ popular science are in ______ short supply.
A. the; a B. /; / C. /; the D. the; the
22.The girl the teachers considered _____ was caught _____ in the exam, which surprised us very much.
A. to be the best; cheating B. as the best student; to cheat
C. being the best; cheating D. as a good student; to cheat
23. The population of Chongqing, _____from the countryside, are making their efforts to build their hometown into a more beautiful and modern society.
A. the majority of which are B. of which the majority is
C. the majority of whom are D. of whom the majority is