练习：
1. According to the passage， which of the following is NOT true？
A. Eating less than usual might make us live longer.
B. If we go on a diet when old， we may keep healthy.
C. Dieting might not be needed.
D. We have to begin dieting from childhood.
2. Why does the author mention an elderly mouse in paragraph 2？
A. To describe the influence of old age on mice.
B. To illustrate the effect of meager food on mice.
C. To tell us how mice’s liver genes behave.
D. To inform us of the process of metabolizing drugs.
3. What can be inferred about completely normally fed mice mentioned in the passage？
A. They will not experience free radical production.
B. They will experience more genetic rejuvenation in their lifetime.
C. They have more old liver genes to behave like young genes.
D. They are more likely to suffer from inflammation.
4. According to the author， which of the following most interested the researchers？
A. The mice that started dieting in old age.
B. 27 of those 46 old genes that continued to behave like young genes.
C. Calorie restriction that works in people.
D. Dieting that makes sure a drug is effective.
5. According to the last two paragraphs， Spindler believes that
A. calorie restriction is very important to young people
B. seeing the effect of a diet， people will eat less than normal.
C. dieting is not a good method to give us health and a long life.
D. drugs do not have the effects of calorie restriction.
答案与题解：
1. D 第一段第一句讲“节食可能不是非做不可的事”，第二句讲“即使上了年纪再节食，我们仍然有可能在很大程度上保持青春活力”，因此，“我们必须从小就开始节食”是错误的，D是答案。
2. B 第二段体积“一只高龄老鼠”的时候，作者谈到，“只要连续四周限制它仅是，它的肝脏基因就会变得和衰老前一样充满活力”。据此，“为了描述节食对老鼠所产生的影响”最好地回答了题干中的问题。
3. D 第四段提到，“正常饲养的老鼠随着年龄的增长有46条肝脏基因会发生变化，这种变化与炎症和身体组织无限激增相关”，因此，D正确。
4. A 第四段最后一个句子讲“但最惊人的发现时那些上了年纪才开始节食的老鼠也能从70%的基因变化中受益”。“最惊人的”自然是“最令研究人员感兴趣的”。
5. C 文章的最后两段谈及Spindler 对节食的看法。首先，他不能肯定节食是否值得。其次，他希望在不久的将来，我们不必解释。所以我们可以退职，他认为节食不是得以健康长寿的好办法。