GWD-8-Q33逻辑求助 - ChaseDream

In order to withstand tidal currents, juvenile horseshoe crabs frequently burrow in the sand. Such burrowing discourages barnacles from clinging 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.

A. Tidal currents do not 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.

P 1：withstand tidal waves, juvenile crabs burrow in sand---->no barnacle population

P 2: fully grown, crabs could withstand waves----> have significant barnacle population

Which can support p 3? According to OEP principle, we read the following choices.

B:Contradict to the P 2, because once the crabs are fully grown, they could hold barnacles on their shells.

Now, let's reconsider choice A and E. Why E is better than A? In fact, when first time encounter A, I find that A has nothing to do with P3, because it just provides you the reason why all crabs could have barnacles on their shells, but not why the juvenile crabs in certain area could not.

E in chinese means: 由于不断地长大，幼年的crabs要不断的丢弃原来的壳，长出新壳。In this way, the barnacles which should be held on the shells of crabs, can not stay on the juvenile crabs shells.

P 1：withstand tidal waves, juvenile crabs burrow in sand---->no barnacle population
P 2: fully grown, crabs could withstand waves----> have significant barnacle population
P 3: juvenile crabs in weak tidal region have no barnacle population.
Which can support p 3? According to OEP principle, we read the following choices.
A:could be a contender, remain to be considered.
B:Contradict to the P 2, because once the crabs are fully grown, they could hold barnacles on their shells.
C: out of scope
D: out of scope
E: contender.
Now, let's reconsider choice A and E. Why E is better than A? In fact, when first time encounter A, I find that A has nothing to do with P3, because it just provides you the reason why all crabs could have barnacles on their shells, but not why the juvenile crabs in certain area could not.
E in chinese means: 由于不断地长大，幼年的crabs要不断的丢弃原来的壳，长出新壳。In this way, the barnacles which should be held on the shells of crabs, can not stay on the juvenile crabs shells.
E provides the exact reason to

-- by 会员 pc123 (2009/6/5 9:25:00)

有个疑问，前面讲到：. Such burrowing discourages barnacles from clinging to their shells. 根据我的理解就是在fully grow之前，barnacles都不会去附着在贝壳上，所以E选项中在长成之前换几次壳都不会影响到bar的多少呀？
求高人指点。

-- by 会员 pazzini10 (2011/5/13 0:06:30)