Oceanographer: To substantially reduce the amount of carbon dioxide in

Question

Oceanographer: To substantially reduce the amount of carbon dioxide in Earth's atmosphere, carbon dioxide should be captured and pumped deep into the oceans, where it would dissolve. The cool, dense water in ocean depths takes centuries to mix with the warmer water near the surface, so any carbon dioxide pumped deep into oceans would be trapped there for centuries.

Which one of the following is an assumption that the oceanographer's argument requires?

(A) Carbon dioxide will dissolve much more thoroughly if it is pumped into cold water than it will if it is pumped into warmer water

(B) Evaporation of warmer ocean water near an ocean's surface does not generally release into the atmosphere large amounts of carbon dioxide

(C) Carbon dioxide dissolved in cool, dense water in ocean depths will not escape back into Earth's atmosphere a long time before the water in which that carbon dioxide is dissolved mixes with warmer water near the surface

(D) It is the density of the water in the ocean depths that plays the main role in the trapping of the carbon dioxide

(E) Carbon dioxide should be pumped into ocean depths to reduce the amount of carbon dioxide in the atmosphere only if the carbon dioxide pumped into ocean depths would be trapped there for hundreds of years

GMATNinja · Accepted Answer

The question asks for "an assumption that the oceanographer's argument  requires ," so we are looking for an answer choice that MUST be true in order for the oceanographer's conclusion to hold.

For a quick recap of his/her argument:

Conclusion : "carbon dioxide should be captured and pumped deep into the oceans"

Reasoning behind the conclusion :

Cool, dense water takes centuries to mix with warmer waters 
 Therefore, CO2 pumped into the deep water will remain there for centuries 
 Therefore, pumping water deep into the ocean will reduce the amount of CO2 in the earth's atmosphere

Let's take a look at (A):
 
The reasoning in the oceanographer's argument depends on cool, dense water  remaining separate  from warmer waters -- it does not say anything at all about how thoroughly CO2 dissolves in either type of water. It is entirely possible for CO2 to dissolve equally in both types of water without any impact on the conclusion of the argument. So long as the warm and cold waters do not mix, the CO2 will remain trapped in the cool water and will not enter the earth's atmosphere.

Because (A) does not HAVE to be true for the conclusion to hold, it is not an assumption required by the argument. Eliminate (A).

The oceanographer's stated goal is "to substantially reduce the amount of CO2 in the earth's atmosphere." Notice that there is no timeline on this goal -- as long as CO2 in the atmosphere is substantially reduced, the goal has been met.

According to the passage, the plan he/she proposes  happens  to keep CO2 trapped in the ocean for hundreds of years, which would meet the intended goal -- but that does not mean that this timeline is REQUIRED by the oceanographer's argument. As  abhishek893rai  pointed out, what if the CO2 remains trapped for 99 years? Then the amount of CO2 in the atmosphere would be reduced, and the conclusion would hold.

Because the argument does not REQUIRE (E), it is not an assumption on which the argument depends.

I hope that helps!

Vigneshwaran93 · Answer

I had a confusion with C and E, Can you please explain Why E and A is not correct?

abhishek893rai · Answer

E is wrong because what if it stays dissolved for next 50 years or 99 years. Doesn't break the conclusion.
A is wrong because is tells that one medium of dissolution is better than the other.
Try negating option C, it breaks the conclusion.

Posted from my mobile device

Doer01 · Answer

Hi,
 Choices except C & E are easy to reject. 
I chose C because it seemed just a little bit better than E. E is not bad either. 
 abhishek893rai  E does say that carbon dioxide will remain dissolved hundreds of years and not 99 or 50 years. I am still not convinced by your reasoning. Could you please elaborate your answer a bit more mate?

robu1 · Answer

Anyone kindly explain why is B wrong option.

ngochuyen1904 · Answer

Argument summary:

Goal : reduce the amount of carbon dioxide in the Earth’s atmosphere
 Plan : Carbon dioxide is captured and pumped deep into the oceans where it would dissolve
   Plan based on the fact that:   
• The cool, dense water in ocean depths takes centuries to mix with the warmer water near the surface
• Carbon dioxide pumped deep into oceans would be trapped there for centuries.

Pre-think:   
Pumping does not make dense water in ocean depths escape back into Earth’s atmosphere before the water in which that carbon dioxide is dissolved mixes with warmer water near the surface
That’s what C is telling us

XyLan · Answer

robu1 , 
  Pre-Thinking:  
Plan: Carbon dioxide is captured and pumped deep into the oceans where it would dissolve.
Goal: reduce the amount of carbon dioxide in the Earth’s atmosphere

Option Analysis:  
 B = Evaporation of warmer ocean water NEAR an ocean's surface does NOT generally release into the atmosphere large amounts of carbon dioxide.

Let's negate B,
!B = Evaporation of warmer ocean water NEAR an ocean's surface DOES generally release into the atmosphere large amounts of carbon dioxide.

Even if warmer ocean water on evaporation DOES release into the atmosphere large amounts of carbon dioxide, the plan to dump CO2 in the deep, cold water is still successful since

1) Cool, dense water takes  centuries  to mix with warmer waters
2) CO2 pumped into the deep water will remain there  for centuries 
3) pumping water deep into the ocean will REDUCE the amount of CO2 in the earth's atmosphere

Play with numbers - 
Let's say, Pumping & dumping lead to 5000 Ton reduction of CO2.
Now, even if the warmer ocean water  NEAR an ocean's surface  (   NOT from the depth of the ocean having cold water   ) on evaporation DOES release large amounts of CO2 - say 1000 Ton - Pumping & Dumping is STILL successful!

Learning  
 If the negation of an Option does NOT necessarily break the conclusion, it's NOT an assumption.

Rashed12 · Answer

Would anyone explain why D is incorrect?

Posted from my mobile device

XyLan · Answer

(D) It is the density of the water in the ocean depths that plays the main role in the trapping of the carbon dioxide

Pre-Thinking:  
 Plan: Carbon dioxide is captured and pumped deep into the oceans where it would dissolve.
Goal: reduce the amount of carbon dioxide in the Earth’s atmosphere

Option Analysis:  
 D = It is the density of the water in the ocean depths that plays the main role in the trapping of the carbon dioxide

Let's negate D,
 !D = It is NOT the density of the water in the ocean depths that plays the  MAIN  role in the trapping of the carbon dioxide
Meaning: the density of the water is NOT the MAIN role (  it could be secondary/tertiary role  ) - Let's say it accounts for ONLY 30% of the occurrence.

Furthermore, NOT the MAIN role  ----does NOT imply ---->  ZERO role.
It simply means: Density is NOT the DOMINANT factor. Use the  Negation-of-the-answer-choices  wisely!

Even if the density of the water accounts for ONLY 30%, the plan is  STILL  successful ----> Pumping&Dumping Works!

Rashed12 , Maybe there are  other factors  such as oceanic currents, movement of tectonic plates, earth's myriad magnetic field or fluttering-of-the-wings-of-the-butterfly. 
Yet, the negation of option-D(  i.e., NOT being the MAIN-factor  ) does NOT  necessarily   BREAK  the conclusion.

Learning  
 Hence, optionD is NOT the assumption.
If the negation of an Option does NOT  necessarily  break the conclusion, it's NOT an assumption.

desertEagle · Answer

The question asks for assumption. What is stated in C is given in the question stem. As far as I know, assumption is unstated statement that should link a premise with the conclusion.

Kindly explain.

Thanks

GMATNinja · Answer

There's a subtle difference between the assumption stated in (C) and the information in the passage.

The passage says that the carbon dioxide will dissolve into the cool, dense water in ocean depths and that it takes centuries for that cool, dense water to mix with the warmer water near the surface.

But what if the carbon dioxide does not   remain   dissolved in the cool, dense water? What if, for example, the carbon dioxide is gradually released from the cool, dense water and bubbles up to the surface? If that happens a long time before the mixing, the argument falls apart.

(C) eliminates that possibility, making it a required assumption.

I hope that helps!

VerbalBot · Answer

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Oceanographer: To substantially reduce the amount of carbon dioxide in

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