#12 - The retina scanner, a machine that scans the web of

[hassan66]

Hi, I was between A and B and ultimately chose B. I understand how A is correct-- if a disease altered the pattern of the blood vessels in the retina, then upon a second scanning, the machine may not recognize this person's retina as having been scanned into the system before because the disease has created a new pattern.

However, I am struggling with B. The stimulus says that no two eyes have identical patterns. So that must mean that the left and right eye of a person have different patterns. But the scanner can still determine if it's scanned a retina by looking at one eye? If you negate B, it says that some people have different patterns in their left and right eye. But based on the stimulus, the scanner can (somehow) determine if it has scanned a retina from that person by even scanning one eye?

[James Finch]

Hi Hassan,

The conclusion in the stimulus states that a retina scanner can successfully identify whether it scanned one or both of a person's retina's before, but doesn't give us a specific parameter. Based on the information in the stimulus that no eyes have the exact pattern, we can determine two things: we can infer that the stimulus assumes that both eyes must be scanned for the conclusion to be true (making this a possible prephrase, but not one of our actual answer choices), and that answer choice (B) is not an assumption--it's explicitly stated that no two eyes have the same retina pattern, which would mean that every person's left eye has a different retina pattern than their right eye. This makes the information in (B) false, according to the stimulus, meaning it can't be the correct answer to this assumption question.

Hope this clears things up!