第一节：单项选择（共15小题，每小题1分，满分15分）
21. AIDS is a disease that the body’s immune system.
A. breaks out B. breaks into C. breaks down D. breaks up
22. He urged that much of the poverty .
A. should wipe out B. wiped out C. be wiped out D. had wiped out
23.They paid a visit to used to a factory.
A. where B. what C. which D. that
