根据下面资料，回答题。 You do not usually get something for nothing. Now, a new -考呗网

公共英语三级

单选题 根据下面资料，回答题。
You do not usually get something for nothing. Now, a new study reveals that the evolution of an improved learning ability could come at a particularly high price: an earlier death.
Past experiments have demonstrated that it is relatively easy through selective breeding to make rats, honey bees and--that great favourite of researchers--fruit flies a lot better at learning. Ani-mals that are better learners should be competitive and, thus, over time, come to dominate a popu-lation by natural selection. But improved learning ability does not get selected amongst these ani-mals in the wild. No one really understands why.
Tadeusz Kawecki and his colleagues at the University of Fribourg in Switzerland have meas-ured the effects of improved learning on the lives of fruit flies. The flies were given two different fruits as egg-laying sites. One of these was laced with a bitter additive that could be detected only on contact. The flies were then given the same fruit but without an additive. Flies that avoided the fruit which had been bitter were deemed to have learned from their experience. Their children were reared and the experiment was run again.
After repeating the experiment for 30 generations, the children of the learned flies were com-pared with normal flies. The researchers report in a forthcoming edition of Evolution that although learning ability could be bred into a population of fruit flies, it shortened their lives by 15%. When the researchers compared their learned flies to colonies selectively bred to live long lives, they found even greater differences. Whereas learned flies had reduced their life spans, the long-lived flies learned less well than even average flies.
The authors suggest that evolving an improved learning ability may require a greater investment in the nervous system which takes resources away from processes that delay ageing. However, Dr.Kawecki thinks the effect could also be a by-product of greater brain activity increasing the produc-tion of Reactive Oxygen Species ( ROS), which can increase oxidation in the body and damage health.
No one knows whether the phenomenon holds true for other animals. So, biologists, at least,still have a lot to learn.
Past experiments prove selective breeding can make animals better__________．

A．commanders
B．competitors
C．survivors
D．learners

参考答案：D进入在线模考

参考译文
人们通常很难不劳而获。如今，一项新的研究显示学习能力的进化需付出相当大的代价：减少寿命。
以往的实验证明人们可以很容易地通过选择性培育提高老鼠、蜜蜂和研究者最爱的果蝇的学习能力。动物中的佼佼者具备更大的竞争力，因此，根据自然选择的法则在动物群中占支配地位。但是在野生环境中，具备这种能力的动物却无法占统治地位，没人理解到底是为什么。
瑞士佛里堡大学的塔德乌什奎克和他的同事们对提高果蝇学习能力的效果进行了测试。在两地产卵处分别给果蝇不同的水果。研究者们给其中一处果蝇抹了苦味添加剂的水果，果蝇只有在接触时才能察觉。之后又给这些果蝇提供了相同的水果，但没有添加剂。会避开苦味添加剂水果的果蝇被认为通过经历提高了学习能力。它们繁殖后代，实验还在继续进行。
在对30代果蝇做反复的实验后，将学习能力强的果蝇后代与普通果蝇后代进行对比。研究者们将结果汇报在即将出版的《进化论》一书中，尽管果蝇成功地将学习能力繁殖到下一代，但是它们的生命却缩短了15％。当研究者们将学习能力强的果蝇与专门培育生命力强的果蝇相比，他们发现了更大的不同。学习能力强的果蝇缩短了它们的生命期限，长命果蝇的学习能力低于普通果蝇。
研究者们推测学习能力的进化可能会需要大量神经系统的活动，这样会加速衰老的过程。然而，奎克教授认为这种影响也可能是大脑活动产生活性氧的副作用，活性氧会增强身体的氧化并损害健康。
没有人知道其他动物是否也会产生同样的现象。因此，生物学家至少还有很多要去研究学习。
【精析】细节题。从文章第二段第一句“Past experiments have demonstrated that it is relatively easy through selective breeding to make rats．honey bees and—that great favourite of researchers--fruit flies a lot better at learning．”可知，实验证明选择性繁殖可以提高动物的学习能力，故选D。

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1 In this experiment，scientists observed that__________．

A．some flies avoided the fruit without an addictive
B．some flies preferred the fruit with an addictive
C．the eggs of the flies were not damaged
D．the impact on the flies did not last long

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2 The forthcoming report says that__________．

A．long-lived flies are better at laying eggs
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3 According to Dr．Kawecki，greater brain activity__________．

A．reduces oxygen consumption
B．regulates the nervous system
C．speeds up the ageing process
D．stabilizes the ageing process

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