21. If the world is to remain peaceful, the utmost effort must be made by nations to limit local ______ .
A. collisions B. contacts C. contradictions D. conflicts
22. As a candidate, you must make a good _____ on everyone you meet if you want to win the election.
A. decision B. situation C. impression D. position
23. In order to ______ a good knowledge of English , he gave up his job and went to study in an English school.
A. require B. inquire C. acquire D. address
