Although exposure to asbestos is the primary cause of mesothelioma, a slow-developing cancer, researchers believe that infection by the SV40 virus is a contributing factor, since in the United States 60% of tissue samples from mesotheliomas, but none from healthy tissue, contain SV40. SV40 is a monkey virus; however, in 1960 some polio vaccine was contaminated with the virus. Researchers hypothesize that this vaccine was the source of this virus found in mesotheliomas decades later.

Which of the following, if true, most strongly supports the researchers' hypothesis?
a. SV40 is widely used as a research tool ini cancer laboratories.
b. changes in the technique of manufacturing the vaccine now prevent contamination with SV40.
c. recently discovered samples of the vaccine dating from 1960 still show traces of the virus.
d. In a small percentage of cases of mesothelioma, there is no history of exposure to asbestos.
e. In Finland, where the polio vaccine was never contaminated, samples from mesotheliomas do not contain SV40.

OA is E
What's the logic here? Is "SV40 virus is a contributing factor" also not a conclusion that we need to weaken? Why is " Researchers hypothesize that this vaccine was ..." the only hypothesis ?

Thanks for your help.

This is a tricky one. Initially I thought the answer was C but on closer reading it's E

Here is my reasoning

Researcher's Hypothesis : vaccine was the source of this virus found in mesotheliomas


POE

A : Irrelevant. How does it matter if it's widely used
B : Irrelevant . Doesnt matter in the current process
C: Close call - keep it
D : Irrelevant. Small percentage of cases doesnt help to strengthen the hypothesis
E : Keep it

Between C and E

Mesothelioma - Primary cause Asbestos
Contributing Factor -SV40
60% of Tissue samples of meso* contain SV40
SV40 - Polio vaccines were contaminated with the virus

Ans C talk about traces of virus found in the vaccine. But doesnt talk about the traces of virus in cases of meso*
There is a scope shift

Ans E Strongly says that vaccine was not contaminated and that samples of meso* did not contain SV40
Which means the only source possible for a tissue affected by meso* to contain SV40 is from the vaccine


I think this is pretty tricky

wait, what? why would you have to weaken anything?
the problem asks you to strengthen the argument, not to weaken it.

you are correct in asserting that there are essentially 2 hypotheses in this passage. however, there are two extremely strong indications that you should only be considering the second one (the final sentence of the passage):
1: none of the answer choices strengthen the assertion that sv40 is a contributing factor.
2: the last sentence starts with 'researchers hypothesize'. since the question prompt refers to a 'hypothesis', you can be pretty sure this is the one.

Need a little help in eliminating (C), please.

Thanks.

(c) doesn't help; it merely confirms what we already know.
specifically:
it tells us that "recently discovered samples of the vaccine dating from 1960 still show traces of the virus."
in other words, choice (c) tells us only that the virus was/is present in some 1960-era vaccines.

the problem is that we already know this: the passage tells us, after all, that "in 1960 some polio vaccine was contaminated with the virus".

(c) adds absolutely nothing new beyond this already-established fact.

thank you.

sure thing

Is it true that since D. says a small percentage we can discard that answer as a strengthener? It seems to me D also strengthens this argument.

My choices boiled down to D and E. Thanks for your time.

Yeah. Small percentage is not very helpful. Could be .0000001%. E is much stronger since it references the population of mesotheliomas in an entire country.

_________________
Jamie Nelson
ManhattanGMAT Instructor

Can someone help clarify the reason why (B) is wrong?

(B) says --> Modified vaccine prevents SV40 contamination. Doesn't this strengthens the fact that the vaccine contained SV40 at first place, which is researcher's hypothesis?

Or is (B) wrong because it says SV40 and doesn't explicitly say SV40 that's in meso..?

Let me help you here as this is one of those rare CRs which I got correct :)

the researchers' hypothesis is:- this vaccine was the source of this virus found in mesotheliomas decades later

Option B -
b. changes in the technique of manufacturing the vaccine now prevent contamination with SV40.

There are 3 problems with this choice -
1. From the passage, we have NO idea about the techniques or the way the vaccine was / is manufactured -- Irrelevant
2. Even if contamination is stopped now, how can it help in emphasizing that the vaccine actually was the contributor ? To stop the use of something does not mean that thing is / was problematic !
3. It doesnt say anything about the relation between mesotheliomas and SV40, or in the first place whether they are even related to polio or not !

Let me know if it helped or not.

that is not the hypothesis here; in fact, that is a known fact. the argument states explicitly that "in 1960 some polio vaccine was contaminated with the virus"; there can be no debate about this fact.

the hypothesis in this argument is that this sv40 -- the sv40 that got into the polio vaccine in 1960 -- is the same sv40 that was found in the cancers later on.
since we are only concerned with whether the 1960 polio vaccine spread the virus, later changes in the procedure for manufacturing the vaccine are irrelevant.

I have totally a different reason why we need to select E:

First let us understand what the argument is about. All that is hypothesized is THE SOURCE OF virus; the argument does NOT INTEND to verify if the virus IS ALSO causing the cancer: it is just taken for granted (i.e., the virus can also contribute) and we can safely ignore it for the discussion.

Now, we need to prove that there is a possibility that the virus could have been due to contaminated vaccine.

We have 3 sets of people:

--> In US, two sets of people: ill people with contaminated vaccine + a virus and healthy people with clean vaccine + NO VIRUS.
--> In Finland, one set of people: ill people with clean vaccine + NO VIRUS.

from those 2 premises, we can conclude that the virus is due to contaminated vaccine and this is exactly what researchers hypothesized in the last sentence.

Note: there could be some other reason for the virus presence, but in the given context we can not eliminate the possibility of contaminated vaccine.

Hope my analogy is correct.

Thanks
Aravind

looks like you have a good understanding of the analysis here..

_________________
Tim Sanders
Manhattan GMAT Instructor

I see prephrasing possible answer/direction is effective on CR.

paraphrasing: vacine creates the virus.
(though argument is complex, it is simple after you sumarise. The first part of the argument is red herring)

prephrasing: look for something which said there is no other cause

goint to answer choices and look for answer choice which is most similar. eliminate A,B,D at the first time reading.
C and E is left.

C is REPEATATION OF EVIDENCE, a strap famous on Strengthening and Assumption questions.

choose E.

Please, comment of my work order.