As we have seen, the focus of medical care in our society has been shifting from curing disease to preventing disease—especially in terms of changing our many unhealthy behaviors, such as poor eating habits, smoking, and failure to exercise. The line of thought involved in this shift can be pursued further. Imagine a person who is about the right weight, but does not eat very nutritious (有营养的) foods, who feels OK but exercises only occasionally, who goes to work every day, but is not an outstanding worker, who drinks a few beers at home most nights but does not drive while drunk, and who has no chest pains or abnormal blood counts, but sleeps a lot and often feels tired. This person is not ill. He may not even be at risk for any particular disease. But we can imagine that this person could be a lot healthier.
The field of medicine has not traditionally distinguished between someone who is merely "not ill" and some one who is in excellent health and pays at
A. keeping people in a healthy physical condition
B. monitoring patients' body functions
C. removing people's bad living habits
D. ensuring people's psychological well-being
Text 4
Although, recent years have seen substantial reductions in noxious pollutants from individual motor vehicles, the number of such vehicles has been steadily increasing. Consequently, more than 100 cities in the U. S. still have levels of carbon monoxide, particulate matter, and ozone that exceed legally established limits. There is a growing realization that the only effective way to achieve further reduction in vehicle emissions—short of a massive shift away from the private automobile—is to replace conventional diesel fuel and gasoline with cleaner-burning fuel such as compressed natural gas, liquefied petroleum gas, ethanol, or methanol.
All of these alternatives are carbon-based fuels whose molecules are smaller and simpler than those of gasoline. These molecules burn more cleanly than gasoline, in part because they have fewer, if any, carbon-carbon bonds, and the hydrocarbons they do emit are less likely to generate ozone. The combust
A. be somewhat lighter in total body weight than a conventional vehicle fueled with gasoline
B. have a larger and more powerful engine than a conventional vehicle fueled with gasoline
C. average more miles per gallon than a "gasoline alone" vehicle fueled with methanol
D. have a larger and heavier fuel tank than a "gasoline alone" vehicle fueled with methanol
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