单项选择题

Questions 27—30

A． A friend of the man’s.
B． An air conditioning expert.
C． A scientist who set out the principles for internal combustion.
D． A professor who invented automobiles and airplane.

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保护土壤的措施可以防止土壤被风吹走，或被水冲走。良好的土层可以为人类和动物提供粮食。[听力原文] Soil conservation efforts protect soil from wind and water that can blow or wash it away. Good soil produces food crops for both people and animals.

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