GMAT Verbal Critical Reasoning
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Author:  questioner [ Sun May 27, 2012 4:19 pm ]
Post subject:  GMAT Verbal Critical Reasoning

Mary Mallon, known as “Typhoid Mary,” was a typhoid “carrier” who was infected with the typhoid bacillus for a prolonged period of time. She developed neither typhoid fever nor its symptoms; however, other people could, and did, develop this disease after contact with her.

Which of the following is best supported by the statements above?

A. Typhoid fever is not always fatal.

B. Typhoid fever is equally communicable whether the person infected with the typhoid bacillus actually has the disease or not.

C. The absence of the usual symptoms of typhoid fever is not always a reliable indicator that one does not have typhoid fever.

D. Typhoid fever sometimes occurs even when the typhoid bacillus is not present.

E. The typhoid bacillus does not always cause typhoid fever.

Correct Answer: E

This is a logic question, which means that you will see answer choices that sound perfect, but contain a minor logical flaw. Mary was a carrier of the typhoid bacillus yet never developed typhoid fever. This statement indicates that infection by the typhoid bacillus did not cause her to develop typhoid; therefore, infection by the typhoid bacillus does not always result in the disease. None of the other choices can be inferred from the passage. Choice (A) is a trap because Mary was infected with the typhoid bacteria, which clearly are not always fatal, but we know nothing about those who get typhoid fever. Similarly, choice (B) would only be inferred if Mary had exhibited symptoms of typhoid fever without contracting the disease; we are told she had neither the disease nor its symptoms. (C) and (D) are not stated or implied in the passage. Mary didn’t have typhoid fever (she was infected with the typhoid bacillus) so it is outside the scope.


Please elaborate more on how (B) can't be an answer. I am not able to understand your explanation here properly.

Author:  Nick [ Sun May 27, 2012 4:20 pm ]
Post subject:  Re: GMAT Verbal Critical Reasoning

Choice (B) says people with the disease are "equally" contagious as those with only the bacteria, but the passage does not give us any way to make this comparison. We are told Mary is contagious and does not have the disease, but this does not reveal whether she would be "equally" contagious if she did have the disease.

In other words, it's possible Mary could be more (or less) contagious if she had the disease or its symptoms. We are told she had neither, so we can't know how her contagiousness compares to those with the disease. All we can absolutely infer from the passage is that the bacteria does not always cause the disease, which is choice (E).

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