Air Pollution and Acid Rain The increasing variety and prevalence of pollution presents the world with many extremely daunting problems, air pollution in particular ranks among the most serious. In the following text, air pollution and acid rain caused by automobiles will be discussed. Certain solutions to the problem will be provided in the conclusion. It is widely known that cars are the main cause of air pollution in cities, accounting for 60% to 90% of all air pollution. This will get worse as the number of cars increases in urban areas. How do cars cause air pollution？ First we must examine how a car works. Theres a mixture of petrol in the cars internal combustion engine which create the force for the automobile to move. Unfortunately, in this process there are some poisonous chemicals which remain; these poisonous chemicals mainly come out of the car through the exhaust, its not just what comes out of the car exhaust that is dangerous, the brake system also causes pollution. Brakes on cars release asbestos, it is a highly dangerous substance and it can kill humans. Also, the tires themselves give off small rubber particles which are not very healthy. Acid rain caused by air pollution has strongly influenced peoples lives. It is almost impossible to describe the mathematical relationship between what goes up as pollutant emissions and what comes down as acid rain. However, we do know the primary source of acid rain is the pollution released by power plants. The pollutants combine with moisture in the atmosphere and then fall as an acid rain. Germans often call it royal water, because it can break down gold. The royal water falls in the form. of rain or snow on the German Black Forest and attacks the soil. Microorganisms within the soil perish and metals harmful to trees like aluminum leak into the ground. At the same time, the acid rain attacks the trees leaves and dissolves their waxy coating. The leaves then shrivel and die. About one in every ten trees in the Black Forest is a fir. 76% of all firs in the Black Forest are dying. 41% of all spruce are diseased, 43% of all pine are diseased, 26% of beech trees and 16% of all other trees are dying. Environmental groups like Green Peace campaign around Europe trying to stop the causes of acid rain. We need to find solutions to this problem. First, we should try and discourage the overuse of cars. We could do this by raising taxes on petrol or by making cars more expensive. Second, we can encourage alternative methods of transportation. For example, in Shanghai recently, a subway has been built underground, which takes some of the pressure off the roads. Some people would rather use the underground than drive their cars. Next, we could develop and use cleaner fuels instead of petrol. For example, we might use natural gas in the future or we might experiment with battery powered cars. Finally, the actual by-products of vehicle emissions must be managed. (A)Scientists and engineers are now trying to use mechanical means for reducing the amount of chemicals that are emitted from cars exhaust pipes. (B)Germany is now leading the way in attacking this part of the problem. (C)In order to clean up motor vehicle emissions, all new cars in Germany must now meet new emission standards and be fitted with a device called a catalytic converter. (D)This is a device that is fixed over the exhaust and controls the carbon monoxide and other dangerous chemicals that cars give off. Like Germany, the United States also introduced strict clean air-controls on motor vehicle emissions in the mid-70s as part of their efforts to reduce acid rain. Its unlikely that any one of these solutions will work on its own. It will take a combination of all four of these solutions to help solve the air pollution problem.
The word daunting in Paragraph 1 is closest in meaning to ______.
A．solvable
B．frightening
C．promising
D．intrepid
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