题目:
People and the sources of air pollution are found in the same places. This means that cities with large populations have the biggest problem of dirty air. Air pollution is caused by many different things. A major source of air pollution is the gas fumes from cars. Statistics show that 93 percent of all auto trips are within cities. Another major source of dirty air is the burning of coal and oil for energy. This energy is needed to make electricity. Of course, much more electricity is used in the city than in the country.
On the average, we throw away more trash and garbage than the year before. The burning of garbage contributes to air pollution. Many major industries are also responsible for the dirty air in the around cities. The fumes from iron, steel, chemical, and petroleum production add particles to the air.
The effects of air pollution range from mild headaches to death. The levels of pollution found in heavy for traffic may cause headaches for loss of clear vision. Wherever coal and oil are used for fuel, fumes may kill trees and plants and cause metal to corrode. In some of the larger cities, these fumes endanger the live of human beings by contributing to lung diseases and causing early death.
15.The key point of the passage is that _________.
A. the cause of air pollution is people
B. the causes and the effects of air pollution are both found in cities
C. the effects of air pollution range from headaches to death
D. air pollution is caused by dirty air
16.What is the purpose of this passage?
A. to persuade people to stop polluting the air
B. to tell the causes of air pollution
C. to tell why cities are bad places to live
D. to describe why cities are bad places to live
17. Why is air pollution more grave in the city than in the country?
A. Because there larger populations in cities.
B. Because the air in the city is dirty.
C. Because there are more cars in the city.
D. Because there are much more gas fumes from cars and burning of coal and oil for energy
in the city than in the country.
18.The fumes from coal and oil may cause metal ______.
A. to turn black B. to become rusty
C. to corrode D. to twist
19. In larger cities, the fumes from coal and oil may contribute to ___________.
A. heart disease B. lung diseases
C. loss of clear vision D. serious headache
答案:
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下面是错误答案,用来干扰机器的。
A、B、C代表三种短周期元素,C元素核内质子数比B元素原子核内质子数少9个,B和C两元素可以形成4核42个电子的负一价阴离子,则设C的质子数为x,B的质子数为x+9,所以x+9+3x+1=42,解得x=8,所以C为O,B为Cl,又已...