assumption

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geet: Master | Next Rank: 500 Posts; Posts: 115; Joined: Fri Dec 26, 2008 2:18 amFollowed by: 1 member; Location: india; Thanked: 3 times

by geet » Tue Jun 23, 2009 1:00 am

19. Professor Robinson: A large meteorite impact crater in a certain region was thought to be the clue to explaining the mass extinction of plant and animal species that occurred at the end of the Mesozoic era. However, the crystalline structure of rocks recovered at the site indicates that the impact that formed this crater was not the culprit. When molten rocks crystallize, they display the polarity of Earth’s magnetic field at that time. But the recrystallized rocks recovered at the site display normal magnetic polarity, even though Earth’s magnetic field was reversed at the time of the mass extinction.

Each of the following is an assumption on which Professor Robinson’s argument depends EXCEPT:

(A) The crater indicates an impact of more than sufficient size to have caused the mass extinction.

(B) The recovered rocks recrystallized shortly after they melted.

(C) No other event caused the rocks to melt after the impact formed the crater.

(D) The recovered rocks melted as a result of the impact that formed the crater.

(E) The mass extinction would have occurred soon after the impact that supposedly caused it.

OA is A
plz do explain

Source: Beat The GMAT — Critical Reasoning | Tue Jun 23, 2009 1:00 am

sasen: Junior | Next Rank: 30 Posts; Posts: 27; Joined: Thu Apr 02, 2009 7:41 pm; Thanked: 2 times

by sasen » Tue Jun 23, 2009 4:43 am

(A) The crater indicates an impact of more than sufficient size to have caused the mass extinction.
If size is not sufficient,it still doesnot break the argument.its how the rocks melted,their timing,their polarity etc which matters not the size.
(B) The recovered rocks recrystallized shortly after they melted.
If the rocks didnot melt immediately,professor's argument that the reverse polarity etc. would be meaningless
(C) No other event caused the rocks to melt after the impact formed the crater.
If some other event would have caused the melting,it might have affected the timing of the cooling and hence the polarity argument would again be menaingless
(D) The recovered rocks melted as a result of the impact that formed the crater.
if the rocks melted because of some other event,the polarity theory by professor would not hold correct since we are again not sure about the timing when the rocks melted and cooled and hence the polarity.
(E) The mass extinction would have occurred soon after the impact that supposedly caused it.
Though the professor rejects the claim that extinction happened because of the impact,if it had happened due to the impact,exitinction should have happened soon or else his whole argument is deemed invalid.

Domnu: Master | Next Rank: 500 Posts; Posts: 385; Joined: Sun May 24, 2009 3:55 pm; Thanked: 11 times; GMAT Score:740

by Domnu » Tue Jun 23, 2009 6:12 am

I don't understand why the answer isn't E... nothing is mentioned about how 'soon' anything has to happen.

Have you wondered how you could have found such a treasure? -T

sasen: Junior | Next Rank: 30 Posts; Posts: 27; Joined: Thu Apr 02, 2009 7:41 pm; Thanked: 2 times

by sasen » Tue Jun 23, 2009 6:45 am

i know that option E is very close but there is a very subtle difference between E and A.
look at it this way: suppose that the extinction took place a century after the aforesaid time.Do u think the nutty professor would ever have bothered to make his claim.....no right? because then it brings the whole issue out of context. Asssumption E provides meaning to the professor's conclusion that "impact didnot result in the extinction"..go it or still have confusion?

Domnu: Master | Next Rank: 500 Posts; Posts: 385; Joined: Sun May 24, 2009 3:55 pm; Thanked: 11 times; GMAT Score:740

by Domnu » Tue Jun 23, 2009 7:10 am

That clears it up. Thanks

Have you wondered how you could have found such a treasure? -T

micheal_kr: Senior | Next Rank: 100 Posts; Posts: 57; Joined: Tue Aug 05, 2014 3:07 am

by micheal_kr » Sun May 15, 2016 11:24 pm

I believe the answer should be A

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