GWD8-33

yzhao1

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

This one has been previously discussed (http://forum.chasedream.com/dispbbs.asp?BoardID=24&ID=76582). Personally, I think both D and E are right. The reason for D is that juvenile crabs with big barnacle can not find food and starve to death. Therefore, the survived juvenile are those that do not have big barnacle.

Can anyone tell me what is wrong with my reasoning?

wycg

以下是引用yzhao1在2006-9-12 21:46:00的发言：

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

This one has been previously discussed (http://forum.chasedream.com/dispbbs.asp?BoardID=24&ID=76582). Personally, I think both D and E are right. The reason for D is that juvenile crabs with big barnacle can not find food and starve to death. Therefore, the survived juvenile are those that do not have big barnacle.

Can anyone tell me what is wrong with my reasoning?

D没有说出来道底有多大的影响.而且decrease the ability of a horseshoe crab to find food到底是根本找不到food都没有说. 相对来讲的话E说的很明显.. 关于E的解释见:http://forum.chasedream.com/dispbbs.asp?BoardID=24&ID=76582

2楼.

yzhao1

多谢!