Prep Test 30. Section 2. Question 22

The folktale that claims that a rattlesnake's age can be determined from the number of sections in its rattle is false, but only because the rattles are brittle and sometimes partially or completely break off. So if they were not so brittle, one could reliably determine a rattlesnake's age simply from the number of sections in its rattle, because one new section is formed each time a rattlesnake molts.

Which of the following is an assumption the argument requires in order for its conclusion to be properly drawn?

(A) Rattlesnakes molt exactly once a year.
(B) The rattles of rattlesnakes of different species are identical in appearance.
(C) Rattlesnakes molt more frequently when young than when old.
(D) The brittleness of a rattlesnake's rattle is not correlated with the length of the rattlesnake's life.
(E) Rattlesnakes molt as often when food is scarce as they do when food is plentiful.


Before looking at the answers, let's figure out what's going on. So we get this hullaballoo that a rattlesnake gets a new section every time it molts. And then we are told that the rattlesnake's sections can determine its age. Putting 2 and 2 together, we can confidently say that a rattlesnake molts at the same interval every time. My first thought when reading this question was, say a rattlesnake molts every year, that'll work.

But careful, because answer choice (A) says that, and that turns out to be wrong. If, say, he molted 3 times a year, like clockwork, we could just add up the sections and divide by three. So he doesn't HAVE to molt once a year. He just needs to molt regularly whenever possible.

Choice (B) is kinda stupid. We don't care what the snake's sections look like, so long as they all perform the same function.

Choice (C) is actually the opposite of what would need to be true. If they're molting at different speeds depending on their age, their sections aren't very reliable indicators of the passage of time. Could you imagine a clock which runs faster in the morning than it does at night? That clock would be really shitty, and so is answer choice (C).

Choice (D) is one of those things that make you go, "hmm," as C & C Music Factory would put it. It is an answer designed to tie in a lot of stuff you read in the stimulus. But remember, the fact that the rattles are brittle doesn't really play into the hypothetical scenerio in which, as the conclusion states, "If they were not so brittle, one could reliably determine the rattlesnake's age..." So we don't care about the fact that they're brittle. Or how brittle they are. Or whether said brittleness is correlated with anything.

Choice (E), if you were paying attention, can be chosen based solely on its Not Wrong-ness. But if we actually read it, which may or may not be a waste of time, we'd see that, yep, they'd have to molt as often when food is scarce as when it is not, simply because they molt at given intervals. If they quit molting when food was scarce, that'd make counting their sections as a way of determining their age pretty darn illogical.

SLAM (E) DOWN!