37.Which of the following does the greatest harm to human's health?
A. PM 10.
B. PM2.5.
C. Dust and dirt.
D. Smoke and liquid droplets.
查看答案
38.What are sources of particulate matter?
All particles found in the air.
B. Various kinds of burning activities.
C. AH types of human activities.
D. Reaction of sunlight and water vapor.
39.Why is PM2.5 the most dangerous to human's health?
A. Because it is a kind of "fine" particle.
Because it is of very small size.
C. Because it is only one-thirtieth the average width of a human hair.
D. Because it can go into and stick to human's lungs.
40.How can we reduce the amount of PM2.5?
A. Use chemicals to clean the air.
B. Decrease all kinds of burnings..
C. Improve crushing or grinding operations.
D. Stop industrial processes
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