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Although the geological record contains some hints

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Although the geological record contains some hints [#permalink]

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Although the geological record contains some hints of major meteor impacts preceding mass extinctions, there were many extinctions that did not follow any known major meteor impacts. Likewise, there are many records of major meteor impacts that do not seem to have been followed by mass extinctions. Thus the geological record suggests that there is no consistent causal link between major meteor impacts and mass extinctions.

Which one of the following assumptions enables the argument’s conclusion to be properly inferred?

(A) If there were a consistent causal link between major meteor impacts and mass extinctions, then all major meteor impacts would be followed by mass extinctions.
(B) Major meteor impacts and mass extinctions cannot be consistently causally linked unless many mass extinctions have followed major meteor impacts.
(C) Of the mass extinctions that did not follow any known major meteor impacts, few if any followed major meteor impacts of which the geological record contains no hints.
(D) If there is no consistent causal link between major meteor impacts and mass extinctions, then not all mass extinctions could have followed major meteor impacts.
(E) There could be a consistent causal link between major meteor impacts and mass extinctions even if not every major meteor impact has been followed by a mass extinction.
[Reveal] Spoiler: OA

Last edited by abhimahna on 03 Sep 2017, 10:09, edited 1 time in total.
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Re: Although the geological record contains some hints [#permalink]

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New post 23 Dec 2016, 02:44
Somebody please explain why option D is wrong and why A is correct?

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Re: Although the geological record contains some hints [#permalink]

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New post 23 Dec 2016, 19:21
rulez161 wrote:
Although the geological record contains some hints
of major meteor impacts preceding mass extinctions,
there were many extinctions that did not follow any
known major meteor impacts. Likewise, there are
many records of major meteor impacts that do not
seem to have been followed by mass extinctions.
Thus the geological record suggests that there is no
consistent causal link between major meteor impacts
and mass extinctions.

Which one of the following assumptions enables the
argument’s conclusion to be properly inferred?

(A) If there were a consistent causal link between
major meteor impacts and mass extinctions,
then all major meteor impacts would be
followed by mass extinctions.
(B) Major meteor impacts and mass extinctions
cannot be consistently causally linked unless
many mass extinctions have followed major
meteor impacts.
(C) Of the mass extinctions that did not follow any
known major meteor impacts, few if any
followed major meteor impacts of which the
geological record contains no hints.
(D) If there is no consistent causal link between
major meteor impacts and mass extinctions,
then not all mass extinctions could have
followed major meteor impacts.
(E) There could be a consistent causal link between
major meteor impacts and mass extinctions
even if not every major meteor impact has been
followed by a mass extinction.


The conclusion is: there is no consistent causal link between major meteor impacts and mass extinctions:
Why is that? because (according to the argument) there were many extinctions that did not follow any known major meteor impacts and there are many records of major meteor impacts that do not cause mass extinctions.

The assumtion: Since many cases contradicting a theory is enough to disprove it. We need not to have cases where the theory is not applicable . so, in our case:to conclude that there is a link, all meteor impacts should be followed by mass extinctions.

AC A

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Re: Although the geological record contains some hints [#permalink]

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New post 23 Dec 2016, 19:44
rulez161 wrote:
Somebody please explain why option D is wrong and why A is correct?


(D) If there is no consistent causal link between
major meteor impacts and mass extinctions,
then not all mass extinctions could have
followed major meteor impacts.

D is wrong because it reverses the relationship. it's not because there is no consistent link between meteor impacts and mass extinctions that not all mass extinctions followed meteor impacts. It is the other way around.

Statement:
if,many known meteor are not followed by extinctions → then, No link exists between ext and meteor

the contrapositive of this is:
if a Link between ext and meteor exists → then, all meteor are followed by extinctions (Answer A)

D is the mistaken reversal of the correct answer , it states:
If, no causal link between major meteor impacts and mass extinctions → then, not all mass extinctions could have followed major meteor impacts.

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Re: Although the geological record contains some hints [#permalink]

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New post 23 Dec 2016, 23:26
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rulez161 wrote:
Somebody please explain why option D is wrong and why A is correct?


In addition to the above explanation, you may find the following structure useful to understand the argument more clearly:

In the subject argument, take:
X = a consistent causal link between major meteor impacts and mass extinctions
Y = all major meteor impacts followed by mass extinctions.

Premise: If X, then Y. (option A)
Can be concluded: If not Y, then not X. (conclusion of the passage)
Thus A is correct.

Option D: If not X, then not Y
Cannot be concluded: If not Y, then not X (conclusion of the passage)
Thus D is wrong.

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Re: Although the geological record contains some hints [#permalink]

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New post 23 Dec 2016, 23:38
thanks sayantanc2k. I agree that A is contrapositive of what is stated in question.
but aren't we asked about assumption and not conclusion?

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Re: Although the geological record contains some hints [#permalink]

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rulez161 wrote:
thanks sayantanc2k. I agree that A is contrapositive of what is stated in question.
but aren't we asked about assumption and not conclusion?


Of course - in the above explanation both Option D and option A are tested whether they could be premise (assumption = missing premise), not conclusion.The conclusion in both cases is the same as that drawn in the original passage.

(In my analysis above, the conclusion has been fixed to that given in the passage. Then I have taken 2 cases - the first considers A as premise and the second considers D as premise. We thus see that D cannot be the premise, but A can. Hence A is the correct answer.)

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Although the geological record contains some hints [#permalink]

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New post 09 Sep 2017, 08:37
this question should not be too hard.
Since options are quite similar, test takers should not read too fast.
C,D,E are out for sure. B is wrong because "unless" does not make sure that there is a causal link. A is right b/c of "all"
If ones read too fast, test takers can pick B rather than A.

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Re: Although the geological record contains some hints [#permalink]

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New post 09 Sep 2017, 23:04
Although the geological record contains some hints of major meteor impacts preceding mass extinctions, there were many extinctions that did not follow any known major meteor impacts. Likewise, there are many records of major meteor impacts that do not seem to have been followed by mass extinctions. Thus the geological record suggests that there is no consistent causal link between major meteor impacts and mass extinctions.

Conclusion: … there is no consistent causal link between major meteor impacts and mass extinctions

Falsification Situation:
1) What if meteor impact triggered environmental changes that eventually caused extinction. The environmental changes took time to develop thus giving the impression that the meteor impact is not the cause of extinction?
2) The geological records are not reliable.

Possible assumptions:
1) The environmental changes that take place due to meteor impact are spontaneous.
2) The geological records are reliable/inconsistent


Which one of the following assumptions enables the argument’s conclusion to be properly inferred?

(A) If there were a consistent causal link between major meteor impacts and mass extinctions, then all major meteor impacts would be followed by mass extinctions.
[This is a Conditional Statement] This is another way of saying
If NOT ALL major meteor impacts would be followed by mass extinction, then there WASN’T a consistent causal link between major meteor impacts and mass extinctions.
This is what the argument says. Therefore, this option can be a possible assumption.


(B) Major meteor impacts and mass extinctions cannot be consistently causally linked unless many mass extinctions have followed major meteor impacts.
The argument is not concerned with the number of mass extinctions. Thus, this option is irrelevant.


(C) Of the mass extinctions that did not follow any known major meteor impacts, few if any followed major meteor impacts of which the geological record contains no hints.
[Negate] Of the mass extinctions that followed any known major meteor impacts, many followed major meteor impacts of which the geological record contains hints.
This information (negated) goes to show that the geological records are reliable and thus bolsters the conclusion. This option cannot be an assumption.


(D) If there is no consistent causal link between major meteor impacts and mass extinctions, then not all mass extinctions could have followed major meteor impacts.
[This is a Conditional Statement] Another way of writing this statement is
If all mass extinctions could have followed major meteor impacts, then there’s a consistent causal link between major meteor impacts and mass extinctions.
This is wrong wrt what the argument says.


(E) There could be a consistent causal link between major meteor impacts and mass extinctions even if not every major meteor impact has been followed by a mass extinction.
This option goes straight against the conclusion drawn and, therefore, it cannot be an assumption.

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Re: Although the geological record contains some hints   [#permalink] 09 Sep 2017, 23:04
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