Hydrocarbons

Expert replies

rohit9359: Senior | Next Rank: 100 Posts; Posts: 66; Joined: Sat Jan 03, 2009 2:05 pm

by rohit9359 » Mon Mar 30, 2009 10:12 am

Q. Most geologists believe oil results from chemical transformations of hydrocarbons derived from organisms buried under ancient seas. Suppose, instead, that oil actually results from bacterial action on other complex hydrocarbons that are trapped within the Earth. As is well known, the volume of these hydrocarbons exceeds that of buried organisms. Therefore, our oil reserves would be greater than most geologists believe.
Which of the following, if true, gives the strongest support to the argument above about our oil reserves?
(A) Most geologists think optimistically about the Earth’s reserves of oil.
(B) Most geologists have performed accurate chemical analyses on previously discovered oil reserves.
(C) Ancient seas are buried within the Earth at many places where fossils are abundant.
(D) The only bacteria yet found in oil reserves could have leaked down drill holes from surface contaminants.
(E) Chemical transformations reduce the volume of buried hydrocarbons derived from organisms by roughly the same proportion as bacterial action reduces the volume of other complex hydrocarbons.

OA is [spoiler](A)[/spoiler]. Please explain.

Thanks,
Rohit.

Source: Beat The GMAT — Critical Reasoning | Mon Mar 30, 2009 10:12 am

anshulseth: Master | Next Rank: 500 Posts; Posts: 145; Joined: Mon Feb 16, 2009 8:41 amFollowed by: 2 members; Thanked: 2 times

by anshulseth » Tue Mar 31, 2009 12:32 am

Tough Nut.
Took me some time.

So stem has four statements.
One is a premise, one is an alternative premise.
One provides comparison between premise and alternative premise.
And the last provides the conclusion.

So, what premise says is that geologists believe oil comes from one source.
Alternative premise says that oil comes from other source.

If other sources are more than the first source, then oil reserves will be more than they thought.

To support it, geologist need to be optimistic abt the earth's reserve of oil.
It doesn't matter which way to implement.

If reserves are more, then it would come out more by a method that leads more.
Thus the answer.

Phew..

Asset

Jose Ferreira: GMAT Instructor; Posts: 99; Joined: Thu Mar 05, 2009 5:14 pmFollowed by: 9 members; Location: NYC; Thanked: 43 times; GMAT Score:800

by Jose Ferreira » Wed Apr 01, 2009 5:59 am

Rohit,

Are you sure that you have the correct OA? Here's how I'd break down the argument.

Most Geologists: Oil comes from transformations of **hydrocarbons derived from buried organisms.** [Call these "HBO"]

Alternative explanation: Oil comes from bacterial action on **other complex hydrocarbons trapped within the Earth.** [Call these "OCH"]

Additional evidence: The volume of OCH is greater than that of buried organisms.

Conclusion: If the Alternative Explanation (oil source = OCH) were true and Most Geologists' belief (oil source = HBO) were false, our oil reserves would be greater.

On a Strengthen question, look for gaps in the argument that a good strengthener might fill in. Here we might notice:

1. Oil comes from "HBO," but the Additional Evidence addresses only "buried organisms."

2. The conclusion addresses "our oil reserves," while the rest of the question discusses oil in general.

3. The Additional Evidence discusses the relative volume of OCH and buried organisms, while the conclusion discusses the relative volume of oil derived from each of these sources.

... and so on.

I'm not sure that Choice A fills in any such gap. The optimistic attitude of Most Geologists shouldn't affect the argument, which deals in facts, not attitudes (if anything, their optimism might make it LESS likely that we'll end up with **more** oil than these geologists expect).

On the other hand, Choice E fills in Gap 3 noted above quite nicely. If we get about the same proportion of oil from HBO as we do from OCH, then it's reasonable to conclude that we'll get a greater volume of oil from a greater volume of OCH than we will from a smaller volume of HBO.

Sound good?

Jose Ferreira
Founder and CEO, Knewton, Inc.
https://www.knewton.com/gmat

adamsmith2009: Senior | Next Rank: 100 Posts; Posts: 36; Joined: Fri Mar 27, 2009 6:53 pm

by adamsmith2009 » Wed Apr 01, 2009 7:49 am

I don't think A is the right answer. To me, C supports the theory that there is an abundance of oil below the Earth's surface.

Rohit, are you surea bout the OA?

rohit9359: Senior | Next Rank: 100 Posts; Posts: 66; Joined: Sat Jan 03, 2009 2:05 pm

by rohit9359 » Mon Apr 06, 2009 2:11 am

Apologies guys.

My source had the wrong answer. I have confirmed, the actual answer is (E).

Thanks for your explanation Jose.

Rohit.

vanessa.m: Master | Next Rank: 500 Posts; Posts: 100; Joined: Tue Aug 05, 2014 3:58 am

by vanessa.m » Sun May 15, 2016 2:10 am

I think that option c is the most appropriate in this case

GMAT Course Reviews

563 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (563 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review