Read the text and answer the multiple-choice question by selecting the correct response. Only one response is correct.
Carbon dioxide constitutes only a small part of the atmosphere. But it has an important function in maintaining the balance between radiation from the sun entering the atmosphere and radiation leaving the Earth. Some of the radiation is absorbed by the Earth and some is radiated back into the atmosphere. Since carbon dioxide in the atmosphere prevents some of the radiation from leaving the atmosphere, the heat remains in the atmosphere. Yet, if the proportion of carbon dioxide in the atmosphere is increased as a result of air pollution, the temperature of the atmosphere may rise with catastrophic consequences.
Q.Which of the following most accurately summarizes the opinion of the author in the text?
(A) Air pollution may upset the balance of nature through excessive levels of carbon dioxide.
(B) Carbon dioxide helps prevent the temperature of the Earth from rising or falling.
(C) Climatic changes brought about by air pollution are likely to be serious.
(D) Increase in levels of carbon dioxide in atmosphere causes air pollution.