Carbon dioxide___________

Câu hỏi: Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer for each of the questions from 35 to 42.
GLOBAL WARMING
National borders have no meaning for the atmosphere. This was demonstrated to the world by the Chernobyl nuclear plant disaster and again by the eruption of Mt. Pinatubo. Whatever enters the atmosphere in one country soon travels around the world. And so, scientists are now worried about the global effects of air pollution. Research shows, in fact, that the earth's atmosphere is changing in ways that could be destructive to life. Pollution could be a major cause of this.
One of the pollutants that is causing the greatest concern is carbon dioxide. It is released into the air when coal or petroleum is burned. Carbon dioxide has always been a part of our atmosphere, the product of certain natural processes. However, in recent decades, the amount of carbon dioxide in the atmosphere has greatly increased. This is the result of an enormous increase in the amount of coal and petroleum burned for fuel.
At the same time, the earth's ability to absorb carbon dioxide has greatly decreased. Absorption of carbon dioxide occurs mainly in areas of thick forest. Those areas are rapidly disappearing as more and more forests are cut down.
The result of the increase of carbon dioxide in the atmosphere is the so- called "greenhouse effect". The carbon dioxide acts like a glass screen, making the sun's heat more intense. There are already signs of global warming, say many scientists.
Over the next century, average temperatures could rise by as much as four degrees centigrade. Such a temperature change could be disastrous. Vast areas, such as the whole central United States, could become too hot and dry for agriculture. Because of the melting of polar ice, the water level of the oceans would rise and many low coastal areas would disappear. For example, large parts of the Netherlands, Bangladesh, and the state of Florida would be under water.
In most of the industrialized countries, there are now laws that limit carbon dioxide released into the air. However, in many other countries, such as India and China, there are no such laws. These countries plan, in facts, to double or triple the amount of coal they burn. They cannot afford to change to other kinds of fuel that pollute the air less. And so, they will be releasing even more carbon dioxide into the air.
Thus, laws passed in the industrialized countries will have little effect on the worldwide situation. Our planet is likely to continue to warm up unless the less- developed countries make some changes, too.
A global disaster can only be avoided by a global solution. The industrialized nations need to "think globally". They need to look beyond their own borders at the needs of the earth as a whole. They must put some of their wealth and technology to work in poorer countries. This may be the only way to clean up our atmosphere and prevent disastrous changes.
Carbon dioxide___________
A. is produced by the burning of coal and petroleum
B. is produced by forests.
C. was produced by the Chernobyl disaster.
D. is no longer produced by natural processes.