21.As Susan stared at ______ piles of plastic in her recycling bin, ______ strong sense of responsibility made her stick to her recycling work.
A.不填;不填 B.不填; a
C.the ; a D.the; the
22.Tom's mother kept telling him that he should work harder, but ______didn't help.
A.he B.which C.it D.one
23.Put yourself in situations where you're forced to communicate in English, ______ you'll see more progress over time.
A.until B.or C.but D.and
24.The United Nations are evaluating the damage caused in Haiti earthquake, while in Chile the government itself ______ the lead role.
A.is taking B.was taking C.took D.had taken
25.What's your opinion of Mr.Li's request that we ______ spend half an hour reading English aloud every morning?
A.would B.should C.must D.could