Stuck with 2 close options - Pl Help!!

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Stuck with 2 close options - Pl Help!!

by gauraku » Mon Jun 25, 2012 11:52 am
Lofgren's disease has been observed frequently in commercially raised cattle but very rarely
in chickens. Both cattle and chickens raised for meat are often fed the type of feed that
transmits the virus that causes the disease. Animals infected with the virus take more than
a year to develop symptoms of Lofgren's disease, however, and chickens commercially
raised for meat, unlike cattle, are generally brought to market during their first year of life.

Which of the following is most strongly supported by the information provided?

A. The virus that causes Lofgren's disease cannot be transmitted to human beings by
chickens.
B. There is no way to determine whether a chicken is infected with the Lofgren's disease virus
before the chicken shows symptoms of the disease.
C. A failure to observe Lofgren's disease in commercial chicken populations is not good
evidence that chickens are immune to the virus that causes this disease.
D. An animal that has been infected with the virus that causes Lofgren's disease but that has
not developed symptoms cannot transmit the disease to an uninfected animal of the same
species.
E. The feed that chickens and cattle are fed is probably not the only source of the virus that
causes Lofgren's disease.

After POE, I am stuck with B and C. I shouldn't question correct answer in GMAT, but I do not agree with either B or C.

B says - "There is no way to determine whether a chicken is infected with the Lofgren's disease"
Premise - "Animals infected with the virus take more than a year to develop symptoms of Lofgren's disease" --- so we do have a way to determine whether chickens are affected if they are not sent to market during 1st year of their life.

C says - "A failure to observe Lofgren's disease in commercial chicken populations"
Premise - "Lofgren's disease has been observed frequently in commercially raised cattle but very rarely in chickens" --- we do observe though rarely.

In such question types, we should be able to prove the answer from the given context.

Pl Help and correct my way of thinking.

Correct answer C.
Source: — Critical Reasoning |

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by Kasia@EconomistGMAT » Mon Jun 25, 2012 1:10 pm
Premise 1: The disease has been observed in cattle and very rarely in chickens
Premise 2: Probably the virus is transmitted by feed
Premise 3: It takes over a year for an animal to develop symptoms
Premise 4: Chickens live shorter because they are killed during the first year of life usually

We are looking for information best supported by the premises above.

Answer A is irrelevant. The text does not speak about humans contracting the disease
Answer B is also out of scope - we don't know if there isn't any other way such as a medical test that can confirm whether an animal is sick, we only know that during the first year of life an animal does not show symptoms of the disease
Answer D - out of scope, the question does not mention that
Answer E - irrelevant, the text doesn't say that
c is correct since it is supported by premises 1,3 ,and 4 - chickens rarely show symptoms because they live too short to be able to develop them. Thus, showing no symptoms does not mean being immune. It only means that there wasn't enough time for the symptoms to develop.
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