Critical Reasoning

Source: eGMAT

A recent examination of the waters of the Southern Ocean showed a substantial increase in pollution levels, which is usually caused by routine oil spills during industrial drilling operations in the area. Last month, an article published in the biannual newsletter of a prominent environmental organization attributed this increase to the operations of Gaston Inc., an oil company with several large deep-water drilling operations. This claim is not undermined by the finding that none of Gaston Inc.'s oil plants in the Southern Ocean had any oil spills, because ____________.

A. most increases in the pollution levels of oceans take place because of deep-water drilling operations
B. oil usually floats several feet below the surface of the ocean rather than at the surface itself
C. pollutants that enter the ocean sometimes take decades to affect the marine environment
D. tankers that transport oil from drilling plants to offshore locations often develop leaks
E. calculated amounts of oil are sometimes deliberately discarded by oil plants to maintain water pressure in the area surrounding the plant

eitijan wrote:Source: eGMAT

A recent examination of the waters of the Southern Ocean showed a substantial increase in pollution levels, which is usually caused by routine oil spills during industrial drilling operations in the area. Last month, an article published in the biannual newsletter of a prominent environmental organization attributed this increase to the operations of Gaston Inc., an oil company with several large deep-water drilling operations. This claim is not undermined by the finding that none of Gaston Inc.'s oil plants in the Southern Ocean had any oil spills, because ____________.

A. most increases in the pollution levels of oceans take place because of deep-water drilling operations
B. oil usually floats several feet below the surface of the ocean rather than at the surface itself
C. pollutants that enter the ocean sometimes take decades to affect the marine environment
D. tankers that transport oil from drilling plants to offshore locations often develop leaks
E. calculated amounts of oil are sometimes deliberately discarded by oil plants to maintain water pressure in the area surrounding the plant

Premise: A recent examination showed an increase in pollution levels -- an increase usually caused by oil spills.
Conclusion: This increase can be attributed to the operations of Gaston Inc., even though none of the company's plants had any oil spills.

To strengthen the conclusion, the correct answer must explain how Gaston's operations could have yielded oil spills that increased pollution levels, even though none of the company's plants had any oil spills.

D: Tankers that transport oil from drilling plants to offshore locations often develop leaks.
Implication:
Tankers transporting oil from Gaston's plants to offshore locations could have yielded oil spills, STRENGTHENING the conclusion that the increase in pollution levels can be attributed to Gaston's operations.

The correct answer is D.

Agreed that the correct answer is D.

But E also seems to imply that Gaston could be implicated.
(E. calculated amounts of oil are sometimes deliberately discarded by oil plants to maintain water pressure in the area surrounding the plant)

Is it because the stimulus states that "none of Gaston Inc.'s oil plants in the Southern Ocean had any oil spills", causing direct contradiction ?

I need some confirmation. Please provide your inputs.

TheGraduate wrote:Agreed that the correct answer is D.

But E also seems to imply that Gaston could be implicated.
(E. calculated amounts of oil are sometimes deliberately discarded by oil plants to maintain water pressure in the area surrounding the plant)

Is it because the stimulus states that "none of Gaston Inc.'s oil plants in the Southern Ocean had any oil spills", causing direct contradiction ?

I need some confirmation. Please provide your inputs.

When answering a strengthen or weaken CR, avoid answer choices with variations of the word some.
some = at least one.
Options with some are generally not strong enough to strengthen or weaken a conclusion.

E can be rephrased as follows:
At least once every 100 years, calculated amounts of oil are deliberately discarded by oil plants to maintain water pressure in the area surrounding the plant.
This statement is not strong enough to strengthen or weaken the conclusion that Gaston caused the recent increase in pollution levels.

Eliminate E.

Moreover:
E suggests that companies OTHER THAN GASTON may have deliberately discarded calculated amounts of oil, WEAKENING the conclusion that Gaston caused the recent increase in pollution levels.
The correct answer must clearly STRENGTHEN the conclusion.
Eliminate E.

GMATGuruNY wrote: When answering a strengthen or weaken CR, avoid answer choices with variations of the word some.
some = at least one.
Options with some are generally not strong enough to strengthen or weaken a conclusion.

E can be rephrased as follows:
At least once every 100 years, calculated amounts of oil are deliberately discarded by oil plants to maintain water pressure in the area surrounding the plant.
This statement is not strong enough to strengthen or weaken the conclusion that Gaston caused the recent increase in pollution levels.

Eliminate E.

Moreover:
E suggests that companies OTHER THAN GASTON may have deliberately discarded calculated amounts of oil, WEAKENING the conclusion that Gaston caused the recent increase in pollution levels.
The correct answer must clearly STRENGTHEN the conclusion.
Eliminate E.

Thanks.

Pretty useful tip on the use of "some".

However, we can then argue against the selection of D on a similar basis. D uses the word "often", which can be interpreted to mean "at least once".

Also, along a line of reasoning similar to yours, D does not specify which company the tankers belong to implying the use of tankers by companies other than Gaston. That would have a weakening effect on D, ruling it out as an answer.

Please clarify.

TheGraduate wrote:Pretty useful tip on the use of "some".

However, we can then argue against the selection of D on a similar basis. D uses the word "often", which can be interpreted to mean "at least once".

often is not the equivalent of some.
often -- which means on many occasions -- is the equivalent of many.

Also, along a line of reasoning similar to yours, D does not specify which company the tankers belong to implying the use of tankers by companies other than Gaston. That would have a weakening effect on D, ruling it out as an answer.

Please clarify.

The wording in E suggests that some oil plants may occasionally discard oil while others do not.
Thus, the information in E might not apply to Gaston.

But common sense tells us that ALL oil plants use tankers to transport oil.
Thus, the wording in the OA applies to all oil plants -- including Gaston.

A better reason to discard E:

The passage indicates that pollution is caused by oil SPILLS.
Thus -- to support the conclusion that Gaston caused the increase in pollution levels -- the correct answer must show that Gaston somehow SPILLED oil.
E discusses the DELIBERATE discarding of oil.
This information does not in any way indicate how Gaston might have ACCIDENTALLY spilled oil.