Question: The retina scanner, a machine that scans the web of tiny blood vessels in the retina, stores information about the pattern formed by the blood vessels. This information allows it to recognize any pattern it has previously scanned. No two eyes have identical patterns of blood vessels in the retina. A retina scanner can therefore be used successfully to determine for any person whether it has ever scanned a retina of that person before.

The reasoning in the argument depends upon assuming that

(A) diseases of the human eye do not alter the pattern of blood vessels in the retina in ways that would make the pattern unrecognizable to the retina scanner
(B) no person has a different pattern of blood vessels in the retina of the left eye than in the retina of the right eye
(C) there are enough retina scanners to store information about every person’s retinas
(D) the number of blood vessels in the human retina is invariant although the patterns they form differ from person to person
(E) there is no person whose retinas have been scanned by two or more different retina scanners

Answer: C
Explanation: On the GMAT's critical reasoning portion, analytical and critical thinking abilities are assessed. To answer clearly, a person must possess strong cognitive abilities.

Premise: A retina scanner is a machine that looks at the network of tiny blood vessels in the retina. It stores information about how the blood vessels are arranged. With this information, it can remember any pattern it has already seen.

The blood vessels in the retina do not look the same in any two eyes.

So, a retina scanner can be used to find out if it has ever scanned a person's retina before.

What could possibly hurt this case? What if the patterns made by the blood vessels in the retina of a person whose retina has already been scanned change over time or because of an eye disease? Would the retina scanner still be able to tell if the person's retina has already been scanned? Definitely not. So, it's safe to assume that the pattern made by blood vessels in the retina doesn't change as a person ages and that eye diseases don't change the pattern made by blood vessels in the retina. A is the right answer based on this.

A: Incorrect
It is an incorrect answer. Based on what was said above, this is the right answer.

B: Incorrect
It is the incorrect choice. This doesn't have to be assumed, since the left eye and right eye are different, and the argument doesn't depend on the fact that the pattern in the left eye's retina is similar to the pattern in the right eye's retina.

C: Correct
It is the right choice. It doesn't matter for the argument above because the conclusion doesn't depend on information being stored about everyone's retina.

D: Incorrect
It is an incorrect choice. The argument is not about how many blood vessels are in a person's retina. Instead, it is about how the blood vessels in a person's retina form patterns that are unique to that person. D is not right.

E: Incorrect
It is an incorrect answer. Nothing to do with the conclusion. As long as the conclusion to the argument above holds, as many retina scanners as possible can scan a person's retina.

“The retina scanner, a machine that scans the web of tiny blood vessels” – is a GMAT Critical question. To answer the question, a candidate can either find a piece of evidence that would weaken the argument or have logical flaws in the argument. GMAT critical reasoning tests the logical and analytical skills of the candidates. This topic requires candidates to find the argument's strengths and weaknesses or the logical flaw in the argument. The GMAT CR section contains 10 -13 GMAT critical reasoning questions out of 36 GMAT verbal questions.

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