The air in the house does not remain fresh very long. It’s because （）
A. the fresh air can’t come into the house
B. there is only a little fresh air coming in and a little waste going out
C. the air in the house can’t remain fresh
D. the house gives off wastes
29（）
A. providing
B. serving
C. supposing
D. leaving
24（）
A. possible
B. necessary
C. unnecessary
D. impossible
The writer creates interest in the first sentence by using （）
A. a funny story
B. romantic imagery
C. a vivid description
D. a precise argument
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