GWD 8-33

xxiaoyan

GWD-8-Q33***:

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.

Which of the following, if true, most helps to explain the surprising finding?

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.[E]

不明白d为什么不对，而且d中A very large barnacle population 与原文found not to have significant barnacle populations, even though they seldom burrow. 相互对应，并不是说在他们身上不会发现barnacle而是 不会有很多的barnacle。

请指正！

paulineliao

怎么没人解答这题?NN帮帮忙呀.

time

The statement is not about the relative populations of crabs abd barnacles. That is, comparing the numbers of the two creatures is not relevant. Letter D makes this comparison.

What is at issue is why young crabs do not have the barnacles one would expect them to have (because the tides are weak, they don't need to burrow and you would expect them to have barnacles).

Letter E explains this by saying that in fact the young crabs have several shells one after the other, so no shell lasts for long, and gives no opportunity for the barnacles to grow.

xxiaoyan

老实说，还不是太明白，请帮忙再讲讲

nickt

这么晚还在,辛苦.

D 没有针对性.

原文理解吗? 有浪的地方,小蟹壳上没有Ban(因为小蟹把自己埋在沙里,这样Ban不容易附在壳上).现象:在浪很小的地方(assumption-小蟹不用埋自己),小蟹也没B.

E:因为小蟹褪壳.