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  3. The cooperative spirit that is present in such pack-hunters as wolves is largely absent from the world of the primate. Competiti

The cooperative spirit that is present in such pack-hunters as wolves is largely absent from the world of the primate. Competiti

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问题    The cooperative spirit that is present in such pack-hunters as wolves is largely absent from the world of the primate. Competitiveness and dominance is the order of his day. Competition in the social hierarchy is, of course, present in both groups, but it is less tempered by co-operative action in the case of monkeys and apes. Complicated, coordinated maneuvers are also unnecessary: sequences of feeding action do not need to be strong together in such a complex way. The primate can live much more from minute to minute, from hand to mouth.
    Because the primate’s food supply is all around it for the taking, there is little need to cover great distances. Groups of wild gorillas, the largest of the living primates, have been carefully studied and their movements traced, so that we know that they travel on average about a third of a mile a day. Sometimes they move only a few hundred feet. Carnivores, by contrast, must frequently travel many miles on a single hunting trip. in some instances they have been known to travel over fifty miles on a hunting journey, taking several days before returning to their home base. This act of returning to a fixed home base is typical of the carnivores, but is far less common amongst the monkeys and apes. True, a group of primates will live in a reasonably clearly defined home range, but at night it will probably bed down wherever it happens to have ended up in its day’s meanderings. It will get to know the general region in which it lives because it is always wandering back and forth across it, but it will tend to use the whole area in a much more haphazard way. Also, the interaction between one troop and the next will be less defensive and less aggressive than is the case with carnivores. A territory is, by definition, a defended area, and primates are not therefore, typically, territorial animals.
    A small point, but one that is relevant here, is that carnivores have fleas but primates do not. Monkeys and apes are plagued by lice and certain other external parasites, but, contrary to popular opinion, they are completely flealess, for one very good reason. To understand this, it is necessary to  examine the life-cycle of the flea. This insect lays its eggs, not on the body of its host, but amongst the detritus of its victims sleeping quarters. The eggs take three days to hatch into small, crawling maggots. These larvae do not feed on blood, but on the waste matter that has accumulated in the dirt of the den or lair. After two weeks they spin a cocoon and pupate. They remain in this dormant condition for approximately two weeks before emerging as adults, ready to hop on a suitable host body. So for at least the first month of its life a flea is cut off from its host species. It is clear from this why a nomadic mammal, such as a monkey or ape, is not troubled by fleas. Even if a few fleas do happen to hop on to one and mate successfully, their eggs will be left behind as the primate group moves on, and when the pupae hatch there will be no host "at home" to continue the relationship.
Why aren’t monkeys and apes troubled by fleas? Because ______.
选项 A、the fleas, when fully developed, are not normally aware where the primates are
B、they do not mind the fleas
C、the harmful type of flea rarely gets onto them
D、the fleas’ relationship with them is important biologically
答案A
解析 见文章最后一段：灵长类动物身上没有跳蚤的原因：跳蚤在最终变成成虫以前要花4个星期的时间，主要呆在动物窝里以动物的排泄物为生，而灵长类动物却在一定范围内不断变换自己的“家庭住址”。
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