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课时提升作业(二十一)
必修5 Unit 1
Ⅰ. 单项填空
1. (2013·宁波模拟) to nuclear radiation, even for a short time, may influence genes in human bodies.
A. Exposed B. Being exposed
C. To expose D. Having exposed
2. When he came back three hours later, they were still sitting on the sofa, ________ in conversation.
A. absorbing B. absorbed
C. to absorb D. to be absorbed
3. (2013·西安模拟)The idea of traveling abroad really a lot of Chinese people.
