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题库 / Prep2007E1-CR-4
A popular beach has long had a dolphin feeding program in which fish are given to dolphins several times a day; many dolphins get as much as half of their food each day there. Although dolphins that first benefit from the program as adults are healthy and long-lived, their offspring have a lower life expectancy than offspring of dolphins that feed exclusively in the wild.
Which of the following, if true, most helps to explain the lower life expectancy of offspring of dolphins feeding at the beach compared to other young dolphins?
Sharks that prey on dolphins are less common in the open seas off the beach than in many other areas of the open seas where dolphins congregate.
Many of the adult dolphins that feed at the beach are females that nurse their offspring there.
The fish given to the dolphins at the beach are the same types of fish that dolphins typically catch in the wild.
Many dolphins that feed at the beach with their offspring come to the beach only a few times a month.
Adult dolphins that feed at the beach spend much less time teaching their offspring how to catch fish in the wild than do other adult dolphins.
感觉E选项也有些牵强，A选项相比还好些，鲨鱼靠近海豚聚集的地方，然后吃掉海豚。而野外捕食的海豚，不那么聚集，所以鲨鱼也少，因而寿命长。
文中有一句话说，已成年的海豚受到了喂食的好处从而更健康长寿，A选项没有将已成年海豚与其子孙后代的关系考虑进去，并且与原文阐述信息相左。
如果是A的话，那么成年的海豚计划中的海豚怎么没有因为聚集而被鲨鱼吃掉呢？？所以A显然是不对的，因为这道题是让成年海豚计划里的海豚和幼年的相比，找出其不同点，独立第三方因素即鲨鱼不是这个不同点，如果它说小海豚容易去open sea 玩耍，成年海豚不去，所以鲨鱼吃了小海豚，这样才算不同点，但文中显然没有指出
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