Critical Reasoning

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.

OA - E Pls explain

Fact is that more the current, more the burrowing of crabs and hence less the barnacles attachment to the shells.
Discrepency is that even if the current was less, which should have increased the barnacles attachment to the shells of the crabs, it was found to be less.



Option A states that tidal currents might not be a reason of dislodging of barnacles from the shells but doesn't explain the discrepency.

Option B helps to increase the discrepency by stating that weak currents increase the attachment of baracles.

Option C says of the variation of tidal currents several times during a day which also doesn't explain the discrepency considering the fact that in areas of weak currents the attachment of barnacles to the shells are less.

Option D speaks of the ability of a crab to find food in respect to the barnacles.

Option E states that the crabs shed their shells several times which can lead to less barnacles attachment. It might be possible that the attachment of barnacles was more and then due to shell shedding the attachment was found to be less. Hence it helps explain the discrepency that even if the currents were weak, the attachment was found less.

crackgmat007 wrote: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.

OA - E Pls explain

First of all, let me thank you for this interesting question. Fortunately I was able to arrive the right answer . Below is my reasoning.

A. Tidal currents do not themselves dislodge barnacles from the shells of horseshoe crabs.->This is already inferred fro the passage since the last sentence proves this very clearly.So this is already true and hecne is not a choice for an answer.

B. Barnacles most readily attach themselves to horseshoe crabs in areas where tidal currents are weakest.--> Again negates what the passage says completely since adult crabs in high current regions still have barnacles attached to them.

C. The strength of the tidal currents in a given location varies widely over the course of a day.--> Out of scope since we are region specific and not "time of day specific".

D. A very large barnacle population can significantly decrease the ability of a horseshoe crab to find food.--> Out of scope since we are not concerned about the food habits since it is not mentioned in the passage.

E. Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year.--> We can use POE to arrive at this answer (I did not use this though). If this option was true then the barnacles will have to keep changing shells whereas in an adult crab it is quite the opposite. We can infer from the passage that the tidal currents have no effect on the Barnacles clinging to the shells. So there has to be another reason. This statement provides that reason and hence is the answer.


Hope I was able to clear your concern. Let me know if you need more elaboration and i will be glad to do so.

I feel the answer will be E