Critical Reasoning

After a number of migrant fishermen at the Rotunda Beach pier got sick from consuming locally fished hermit crabs, the Rotunda Beach city authorities posted signs cautioning against the consumption of the crabs. Tests revealed that the crabs were high in prestic acid, a dangerous chemical. But a marked decline in the number of goldfish found by the beach has led to the removal of the warning signs.

Which of the following, if true, would best explain the removal of the signs?

A) Goldfish found off Rotunda Beach cause hermit crabs to excrete prestic acid.
B) The amount of prestic acid produced by an individual goldfish has a direct positive correlation with the density of the goldfish population in that goldfish's immediate vicinity.
C) Goldfish consume various parasites that often contain prestic acid.
D) Rotunda Beach is notoriously polluted.
E) Goldfish would not be able to inhabit the waters off Rotunda Beach if those waters were not saturated with a precise mixture of acids, including prestic acid.

OA after some discussion.

Not sure, but none of the answer choices look right to me.

did you transcribe choice B correctly? I think B would've been correct had it said amount of acid produced by an individual crab.

What is the source and OA?

OA : B

Experts can you please help with this one.

charu_mahajan wrote:After a number of migrant fishermen at the Rotunda Beach pier got sick from consuming locally fished hermit crabs, the Rotunda Beach city authorities posted signs cautioning against the consumption of the crabs. Tests revealed that the crabs were high in prestic acid, a dangerous chemical. But a marked decline in the number of goldfish found by the beach has led to the removal of the warning signs.

Which of the following, if true, would best explain the removal of the signs?

A) Goldfish found off Rotunda Beach cause hermit crabs to excrete prestic acid.
B) The amount of prestic acid produced by an individual goldfish has a direct positive correlation with the density of the goldfish population in that goldfish's immediate vicinity.
C) Goldfish consume various parasites that often contain prestic acid.
D) Rotunda Beach is notoriously polluted.
E) Goldfish would not be able to inhabit the waters off Rotunda Beach if those waters were not saturated with a precise mixture of acids, including prestic acid.

OA after some discussion.

The purpose of the signs was to prevent people from eating the local crabs, which were infested with prestic acid.
The removal of the signs implies that the local crabs are no longer infested with prestic acid.
Since the only change has been a marked decline in the number of goldfish, there must be a link between the NUMBER OF GOLDFISH goldfish and the PRESTIC ACID that had been found in the crabs.

This link is supplied by B:
The amount of prestic acid produced by an individual goldfish has a direct positive correlation with the density of the goldfish population in that goldfish's immediate vicinity.
In other words, fewer goldfish = less prestic acid.

The correct answer is B.

Thanks a lot Mitch.

[quote="GMATGuruNY"][quote="charu_mahajan"]After a number of migrant fishermen at the Rotunda Beach pier got sick from consuming locally fished hermit crabs, the Rotunda Beach city authorities posted signs cautioning against the consumption of the crabs. Tests revealed that the crabs were high in prestic acid, a dangerous chemical. But a marked decline in the number of goldfish found by the beach has led to the removal of the warning signs.

Which of the following, if true, would best explain the removal of the signs?

A) Goldfish found off Rotunda Beach cause hermit crabs to excrete prestic acid.
B) The amount of prestic acid produced by an individual goldfish has a direct positive correlation with the density of the goldfish population in that goldfish's immediate vicinity.
C) Goldfish consume various parasites that often contain prestic acid.
D) Rotunda Beach is notoriously polluted.
E) Goldfish would not be able to inhabit the waters off Rotunda Beach if those waters were not saturated with a precise mixture of acids, including prestic acid.

OA after some discussion.[/quote]

The purpose of the signs was to prevent people from eating the local crabs, which were infested with prestic acid.
The removal of the signs implies that the local crabs are no longer infested with prestic acid.
Since the only change has been a marked decline in the number of goldfish, there must be a link between the NUMBER OF GOLDFISH goldfish and the PRESTIC ACID that had been found in the crabs.

This link is supplied by [spoiler]B[/spoiler]:
[i]The amount of prestic acid produced by an individual goldfish has a direct positive correlation with the density of the goldfish population in that goldfish's immediate vicinity.[/i]
In other words, fewer goldfish = less prestic acid.

The correct answer is [spoiler]B[/spoiler].[/quote]

[b]Why not E?

As E says that Goldfish will only inhabit the Beach if waters contain a good amount of prestic acid. And as the number of goldfish is declining then it can be inferred that the quantity of the acid is reducing. So, the sign is removed.

What is wrong in this logic? Please clarify.[/b][color=darkblue][/color]

Yess !! Even I thought that way earlier and hence was confused.

BUT...If we read the question more carefully - Which of the following, if true, would best explain the removal of the signs?
The question is NOT - Which of the following, if true, would best explain the decline in number of gold fish?

So we are not really bothered why the gold fish declined. But when the number declined, why did they remove the signs or why was it safe to consume crabs.

Does this makes sense now? It did make sense to me, after I gave it a little thought.

=

ranjeet75 wrote:

GMATGuruNY wrote:

charu_mahajan wrote:After a number of migrant fishermen at the Rotunda Beach pier got sick from consuming locally fished hermit crabs, the Rotunda Beach city authorities posted signs cautioning against the consumption of the crabs. Tests revealed that the crabs were high in prestic acid, a dangerous chemical. But a marked decline in the number of goldfish found by the beach has led to the removal of the warning signs.

Which of the following, if true, would best explain the removal of the signs?

A) Goldfish found off Rotunda Beach cause hermit crabs to excrete prestic acid.
B) The amount of prestic acid produced by an individual goldfish has a direct positive correlation with the density of the goldfish population in that goldfish's immediate vicinity.
C) Goldfish consume various parasites that often contain prestic acid.
D) Rotunda Beach is notoriously polluted.
E) Goldfish would not be able to inhabit the waters off Rotunda Beach if those waters were not saturated with a precise mixture of acids, including prestic acid.

OA after some discussion.

The purpose of the signs was to prevent people from eating the local crabs, which were infested with prestic acid.
The removal of the signs implies that the local crabs are no longer infested with prestic acid.
Since the only change has been a marked decline in the number of goldfish, there must be a link between the NUMBER OF GOLDFISH goldfish and the PRESTIC ACID that had been found in the crabs.

This link is supplied by B:
The amount of prestic acid produced by an individual goldfish has a direct positive correlation with the density of the goldfish population in that goldfish's immediate vicinity.
In other words, fewer goldfish = less prestic acid.

The correct answer is B.

Why not E?

As E says that Goldfish will only inhabit the Beach if waters contain a good amount of prestic acid. And as the number of goldfish is declining then it can be inferred that the quantity of the acid is reducing. So, the sign is removed.

What is wrong in this logic? Please clarify.

The CONVERSE of If A, then B is If B, then A.
The converse of a conditional statement is NOT necessarily true.

To illustrate:
If John is in New York City, then John is in the United States.
The statement above is true.
But the CONVERSE - If John is in the United States, then John is in New York City -- is NOT necessarily true.

According to E, if the waters lack sufficient prestic acid, then the goldfish will not inhabit the beach.
We CANNOT infer the converse of this statement.
It is NOT necessarily true that, if the goldfish do not inhabit the beach, then the waters lack sufficient prestic acid.
There could be MANY OTHER REASONS for the decline in the number of goldfish.
Hence, E doesn't offer sufficient justification for the removal of the signs.