单项选择题

Passage One 
Questions 1 to 5 are based on the following passage.  
    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 (烟尘) from cars. 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 leads to air pollution. Many major industries are also the cause of the dirty air in and around cities. The fumes from iron, steel, chemical, and petroleum production add particles (粉尘) to the air. 
The effects of air pollution range from mild headaches to death. The levels of pollution found in heavy traffic may cause headaches for loss of clear sight. Wherever coal and oil are used for fuel, fumes may kill trees and plants. In some of the larger cities, these fumes endanger the lives of human beings by leading to lung diseases and causing early death.

From the passage, we know that （）

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