单选题 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 previous year. 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.
Therefore, it"s high time to stop making our living places unsuitable to live and killing ourselves.

单选题 The key point of the passage is that ______.

单选题 What is the purpose of this passage?

单选题 What is the main cause of more serious air pollution in the city than in the country?

单选题 The fumes from coal and oil may cause metal ______.

单选题 The fumes from coal and oil may cause problems for people in different ways EXCEPT that ______.