Although the geological record contains some hints

Question

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.

sayantanc2k · Accepted Answer

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.

KarishmaB · Answer

Argument:

There are some hints of mass extinctions after meteor impacts.
There were many extinctions that did not follow any known major meteor impacts. 
There are many records of major meteor impacts that do not seem to have been followed by mass extinctions.

(Basically, the argument is saying that though some mass extinctions happened after major meteor impacts, many mass extinctions did not happen after known meteor impacts. Also, many meteor impacts were not followed by mass extinctions. )

Conclusion: So, record suggests that there is no consistent causal link between major meteor impacts and mass extinctions.

We want the conclusion to be properly drawn. So if we take the correct option to be true, it MUST lead to the conclusion to be true. 
Let's see what happens when we take each option to be true.

(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.

If condition - If A (consistent causal link between major meteor impacts and mass extinctions) then B (all major meteor impacts would be followed by mass extinctions)
A implies B
Not B implies not A.

It is given to us that all major meteor impacts were not followed by mass extinctions. There were many major meteor impacts that were not followed by mass extinctions. So it is given to us that B is not true. So 'Not B' is given to us. 
Not B implies Not A.

So we CAN CONCLUDE that there is no consistent causal link between major meteor impacts and mass extinctions. This is the conclusion of our argument. We can conclude the conclusion if we take this option to be true. 
Hence (A) is the answer.

(B) Major meteor impacts and mass extinctions cannot be consistently causally linked unless many mass extinctions have followed major meteor impacts.

This tells us that "Many mass extinctions have followed major meteor impacts" is necessary for "consistently causally linking major meteor impacts and mass extinctions". We do know that some mass extinctions have followed major meteor impacts. Have many mass extinctions followed major meteor impacts, we don't know.

(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.

Doesn't help us conclude that there is no consistent causal link. We don't know when can we establish whether there is a consistent causal link or not. Option (A) defines when there is a consistent causal link.

(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.

If condition - If A (NO consistent causal link between major meteor impacts and mass extinctions) then B (not all mass extinctions could have followed major meteor impacts)
A implies B
Not B implies not A.

We need to establish A (NO consistent causal link between major meteor impacts and mass extinctions). With an if condition, nothing establishes A. We can establish B or 'not A'. 
Hence, this option is incorrect.

(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 is premise against our conclusion.

Answer (A)

rulez161 · Answer

Somebody please explain why option D is wrong and why A is correct?

louwi · Answer

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

louwi · Answer

(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.

rulez161 · Answer

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

sayantanc2k · Answer

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.)

chesstitans · Answer

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.

subrataroy0210 · Answer

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 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.
   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.
   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.

rashwiniyer · Answer

Someone please explain why it is 'A'. I ruled out A because it has an extreme word 'All'. Moreover, the argument concludes that there is no consistent link when there are many instances when meteor did not precede mass extinction and vice versa. But may be for fewer such instances.

abhi2707 · Answer

A  seems very strong due to 'ALL', which is not necessarily a logical negation of 'MANY'.
While D fits the assumption directly if we concentrate on the conclusion.

Umang Agarwal · Answer

A & B look similar and A requires that ALL major meteor impact be followed by mass extinctions whereas be required many mass extinctions follow major meteor impact to establish a link.
Hence B should be right and not A , which is a very extreme conditional statement

Posted from my mobile device

unraveled · Answer

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?

The use of 'many' gives us some exceptions that leads us to believe that there's not causal link.

(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. - CORRECT. Doesn't look attractive since it is claiming 'all'. But that's true.
(B) Major meteor impacts and mass extinctions cannot be  consistently causally linked unless  many mass extinctions have followed major meteor impacts. - WRONG. Tough to eliminate. But using 'unless' suggests it is necessary to follow which is nowhere conclusive from argument.
(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. - WRONG. Limited scope that is not at all concerned about the core of the argument.
(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. - WRONG. It goes beyond the argument giving us a possibility in the future.
(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 . - WRONG.

Answer A.

jackthedanny · Answer

Since we are talking causal relation relationship, a mandatory word like ‘would’ is more appropriate as it is in Option A

To understand this, try replacing ‘could’ with ‘would’ in Option D and read it then.

There has gotta be difference in sentence that only have a difference of ‘would’ and ‘could’.

Posted from my mobile device

lewdtoucan · Answer

Hello,

Adding a helpful pointer that some might find useful: this question is asking for a sufficient assumption.

A sufficient assumption (SA), which I believe is less commonly tested on GMAT than on LSAT, is an assumption that helps prove the conclusion 100% true. More likely than not, sufficient assumptions are required to contain "strong" or "extreme" words to prove the conclusion true.

A necessary assumption, which is more far more common on the GMAT, is an assumption that has to be true given that the necessary assumption is true. The negation technique works well for such questions.

So takeaway: for SA questions, you are necessarily looking for choices with strong language and can't be the reason for elimination.

lewdtoucan · Answer

If this were a necessary assumption question,  would option C be correct?

My reasoning:

conclusion: no causal link between ME and MI.

Opt C states that of the mass extinctions (ME) that did not follow after a meteor impact (MI), very few followed the ME that have no geological records.

if the conclusion is true, then the assumption must be true.

If opt C is not true, then we have of the ME that did not occur after MI, many followed MI which don't have geological records. this serves to call the evidence (geological evidence) into question. Therfore, C when negated doesn't allow the conclusion to be true.

JuniqueLid · Answer

This is a good follow up question. I had the same question but the catch, as someone mentioned above, falls upon the word "consistent" and partial explanation. Personally, I think this is a VERY VERY TRICKY question and uncommon in GMAT based on what the experts said on this forum.

Here is my thinking.

Option (C) seems to be akwardly worded so if I rephrase and simply it, it basically says "if a mass extinction didn't follow a KNOWN major meteor impact, it's unlikely to have followed an UNKNOWN one". This helps rule out the possibility that "a consistent causal relationship actually exists, just that we don't have complete information to prove it". In which case, we seem to be able to draw the stem conclusion that there is no consistent causal link.

Also by negating the original statement, which is "if a mass extinction didn't follow a KNOWN major meteor impact, it could have followed one that is UNKNOWN by human yet". This undermines the conclusion. Therefore, I'm inclined to confirm that this is an assumption.

What's wrong with this - it addresses only one side of the evidence. Some mass extinctions didn't follow a known impact but what about the other evidence: some impacts have not been followed by mass extinctions? That is, if all mass extinctions actually followed a meteor impact (some we know and some we don't), ME can be seen as a subset of MI. We cannot rule out the possibility that there still are many MI that have not been followed by a known ME have actually been followed by an unknown one. The stem conclusion "no consistent causal link" cannot be properly drawn.

Because of the partiality, even when the statement in  (C) is a necessay assumption for the stem conclusion, it is not a sufficient one .

In fact, option  (A) is a sufficient assumption but not a necessary assumption  - if we negated (A), which is "Even if there were a consistent causal link,  not all  major meteor impacts would need to be followed by mass extinctions", the stem conclusion still holds because it emphsises "consistent" causal relationship - a causal relationship that doesn't hold all the time is not consistent. So negating A does not break the conclusion.

This feels like too much overthinking and the counterpositive method people suggested to get to answer (A) is what I'll remember and use in the exam. Am I convinced that (A) is definitely the best answer? Still No.

rishabh1105 · Answer

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.
Makes sense. This needs to be assumed for the premise to conclusion.

(B) Major meteor impacts and mass extinctions cannot be consistently causally linked unless many mass extinctions have followed major meteor impacts.
This would weaken the conclusion as the statement already said that some of the mass extinctions were preceded by major meteor impacts. So then it should be consistently causally linked

(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.
Lets say no records were missed, the argument would still hold true.

(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.
Notice the "not all mass extinctions could have followed major meteor impacts." - the argument discusses about the effect of major meteor impacts and not in opposite direction.

(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.
Weakens the argument. Not an assumption required

Although the geological record contains some hints

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Although the geological record contains some hints

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