Although the geological record contains some hints

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.

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

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

(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.

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.)

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.

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.

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.

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.

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

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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)
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[quote="rulez161"]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.
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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’.

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