In order to withstand tidal currents, juvenile horseshoe crabs frequently burrow in the sand. Such burrowing discourages barnacles fromclinging to their shells. When fully grown, however, the crabs can readily withstand tidal currents without burrowing, and thus they acquire substantial populations of barnacles. Surprisingly, in areas where tidal currents are very weak, juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow.
Which of the following, if true, most helps to explain the surprising finding?
(A)Tidal currents donot themselves dislodge barnacles from the shells of horseshoe crabs.
(B)Barnacles most readily attach themselves to horseshoe crabs in areas where tidal currents are weakest.
(C)The strength of the tidal currents in a given location varies widely over the course of a day.
(D)A very large barnacle population can significantly decrease the ability of a horseshoe crab to find food.
(E)Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year.
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OA---E
粗略分析：1.未成年的马蹄蟹经常埋在沙子里以抵抗潮汐 2.埋到沙子里就阻止了B附着在螃蟹壳上 3.成年蟹有足够力量不用埋起来了，因此上面应该附着大量的B 4.奇怪的是，在潮汐非常弱的地区，马蹄蟹在不埋起来的情况下也没有被大量的B附着。这里2和4构成了paradox，意思是说按1和2，幼年的蟹在潮汐非常弱的地区不用埋起来，应该会附着大量的B，但是4说没有附着，由此选E
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但是，这样看题目仍有无法解释的东西：既然选了E，那么如何解释在潮汐弱的地区，成年蟹身上也没有B附着呢？？？？
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发表于 2011-2-25 17:18:49
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