译成中文也没懂！

Xiaotongdi

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?

1. Tidal currents do not themselves dislodge barnacles from the shells of horseshoe crabs.
   
   
2. Barnacles most readily attach themselves to horseshoe crabs in areas where tidal currents are weakest.
   
   
3. The strength of the tidal currents in a given location varies widely over the course of a day.
   
   
4. A very large barnacle population can significantly decrease the ability of a horseshoe crab to find food.
   
   
5. Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year.
   答案是E！没懂！
   

kikisunflower

现象（论据）：为了避免被潮汐带到海里，小螃蟹要打洞，所以barnacle很难贴在壳上。小螃蟹长大了，不打洞了，壳上就可以粘很多barnacle。

但是作者观察到，潮汐很弱的地方壳上粘的barnacle也不多。

就说明挖不挖洞，只能是barnacle粘在壳上的必要非充分条件，还其他的原因影响壳上barnacle的量。

A. 削弱
B. 削弱
C. 无关
D. 这个选项有点迷惑，如果大量的barnacle会减弱crab的捕食能力，那么有大量barnacle的crab就很有可能挂掉，从而导致剩下的crab身上都没多少barnacle了。但是题目没这么说，don't go out of scope.
E. crab一年就要换好几次壳，长在上面的barnacle在换壳的时候被甩掉了~

Xiaotongdi

如果考试的时候出现这种完全不懂的，或者脑子不转了，咋办啊！

kikisunflower

不会的不会的，要相信女银的直觉~

ahasusanna

不会的不会的，要相信女银的直觉~

-- by 会员 kikisunflower (2011/5/5 15:46:54)

哈哈哈~~~觉得这个回帖好好笑