The questions in this group are based on t

题目：

The questions in this group are based on the content of a passage. After reading the passage, choose the best answer to each question. Answer all questions following the passage on the basis of what is stated or implied in the passage.

Pretty much everybody agrees that clean air is a good thing, right Evidently not so. Since the 1960s, when people started talking about clean air in the first place, the American energy industry, which includes coal companies, oil companies, and utility companies, has dragged its heels on every initiative to improve the quality of the air we breathe. Even after the Clean Air Act of 1970 and its amendments in 1977 and 1990 made it clear that controlling air pollution is a national priority, these companies have found tricks and loopholes to avoid compliance.

Perhaps the most egregious loophole is the one that allows older power plants to disregard limits on sulfux dioxide emissions until they undergo a major renovation, at which point they have to comply. Sulfur dioxide from coal-burning power plants is the primary cause of acid rain in North America. The Clean Air Act states that when coal-burning power plants upgrade their equipment, they must then comply with sulfur dioxide limitations by either installing scrubbing equipment that cleans the emissions or using fuel with lower sulfur content. The law tied the timing of compliance to major renovations in order to give power plants a grace period in which to comply. Many power plants, however, have exploited a loophole in this law by instituting a series of "minor" renovations that, in effect, upgrade their equipment without requiring them to comply with the Clean Air Act. Some plants have cheated the system by undergoing "minor" renovations for decades.

The power companies claim that they have to resort to these underhanded measures because the cost of compliance with the Clean Air Act is too high. And if everyone else is cheating the system, why should they have to install costly sulfur dioxide scrubbers

This cost argument falls apart upon scrutiny. Since 1977, more than 400 power plants across the country have managed to comply with the restrictions and are still making money. The sulfur dioxide scrubbing equipment has turned out to be far less expensive than the power industry naysayers claimed it would be. Many power plants have even complied with the emissions limits and reduced their operating costs by switching from high-sulfur Appalachian coal to the low-sulfur coal produced in western states such as Wyoming and Idaho. Western coal is not only cleaner than eastern coal, but also, because it is generally closer to the surface, as much as 30 percent less expensive to extract.

Clearly, the costs of compliance with the Clean Air Act can be justified, but if these companies were honest, such justifications would not have to be made. If they were honest, they would acknowledge the costs of not complying: the health costs of increased rates of asthma and lung cancer in high-emissions areas; the environmental costs of acid-scarred forests and lakes; the aesthetic costs of a haze of sulfur dioxide cutting visibility across the eastern United States to only half of what it was in pre-industrial times. When you look at the true costs you have to ask, is any cost too high for clean air

The author most likely begins and concludes the passage with questions for what reason ？（）

A. To suggest possible areas for current and future research

B. To pose a question that is answered in the body of the passage, and then to formulate a question that arises naturally out of the discussion

C. To gain the readers’ attention and encourage their agreement with the arguments in the passage

D. To suggest through rhetorical questions that the problems described in the passage do not actually have answers

E. To test the readers’ knowledge of the material discussed in the passage