Usually a meteorological observatory (气象台) _____ air quality in urban areas from one to five: excellent, fairly good, slightly polluted, poor, and dangerous.
24. After ______ seemed a long time, Mr. Li stood up and broke the silence.
23. Allow others the space to voice their opinions, ______ they are different from yours.
20. Could ______ that have a say in the decision do us a favor about the problem?
19. Which do you enjoy ______ you weekend, doing sports or watching TV?
18. She ______ stop whomever she met to tell the story about her Ah Mao.