2. 外语
  3. Animals live longer when their calorie intake is restricted to two-thirds of what is considered normal for their species. Animal

Animals live longer when their calorie intake is restricted to two-thirds of what is considered normal for their species. Animal

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问题 Animals live longer when their calorie intake is restricted to two-thirds of what is considered normal for their species. Animals so restricted are also generally healthier: most disease, including cancer, diabetes, and neurodegenerative illness, are forestalled. Q2This phenomenon was long attributed to a simple slowing of metabolism (cells’ production of energy from fuel molecules) and consequent reproduction of its toxic by-products in response to less food. In fact, however, calorie restriction does not slow mammalian metabolism, and Q1in yeast and worms, metabolism is both sped up and altered. Some scientists now theorize that calorie restriction is a biological stressor that, like natural food scarcity, induces a more complex defensive response, which in mammals includes changes in cellular defenses and repair.
In the passage, the function of the highlighted portion is to
选项 A、Provide specific examples of organisms whose longevity does not increase in response to calorie restriction.
B、Illustrate the probable means by which organisms placed on a calorie-restriction diet compensate for the reduction in available food-based level.
C、Suggest the mechanism that is responsible for prolonging the life of organism whose calorie intake is significantly reduced.
D、Give an example that explain why scientists’ thinking about the physiological effects of calorie restriction changed.
E、Distinguish the different ways that mammalian and non-mammalian metabolisms respond to significant reductions in calorie intake
答案D
解析 本题定位在第四句。本句话的功能是用来反驳之前的老观点，而高亮部分的酵母菌和蠕虫相当于起到反驳作用的例子。因此D正确。
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