Self-study
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. ██ ██ ████ ████ ███ ██ ████████ ███ █████ ████████ █████████ █ █████████████ ███ ██████ ████ ███ ██████ ██ ████████ ██ ███ ███████ ███████ ███ ███ ███████ ██ ██████ ████ ████ █ ███████████ ██████
Argument Summary
The author starts by telling us that the folktale about determining a rattlesnake's age from its rattle sections is false. But she says it's false only because rattles are brittle and can break off.
From there, the author concludes that if rattles weren't brittle, you could reliably determine a rattlesnake's age just by counting rattle sections. The reason? Each time a rattlesnake molts, it gains one new section.
So the logic is: molting adds sections, and if those sections never broke off, you could count them and figure out the snake's age.
Count Sections, Know Age?
The premise tells us that each molt adds one section. That means counting sections tells you how many times a snake has molted. But the conclusion goes further: it says you could determine the snake's age from those sections. That's a leap. The author is treating number of molts as a reliable indicator of age. But is it?
For the method to work, molting has to track age in some predictable way. It doesn't have to be exactly once per year. It could be twice per year, or three times every two years. As long as the rate is consistent, you can work backwards from the section count to figure out the snake's age.
If molting is predictable:
Example: 1 molt per year
Age 1
→ 1 section
Age 2
→ 2 sections
Age 3
→ 3 sections
age = sections ÷ 1
Example: 2 molts per year
Age 1
→ 2 sections
Age 2
→ 4 sections
Age 3
→ 6 sections
age = sections ÷ 2
Either way, a consistent rate lets you work backwards from sections to age. ✓
If molting is unpredictable:
Age 1
→ 1 section (molted once)
Age 2
→ 4 sections (molted 3 times!)
Age 3
→ 5 sections (molted once)
No consistent rate → can't work backwards from sections to age. ✗
So the author must assume that molting happens at a predictable, age-correlated rate. She must also assume that, brittleness aside, nothing other than molting can change the number of sections in a rattle. If some other factor could add or remove sections, the count wouldn't reflect molts alone, and the whole method would break down for a different reason.
22.
Which one of the following ██ ██ ██████████ ███ ████████ ████████ ██ █████ ███ ███ ██████████ ██ ██ ████████ ██████
a
Rattlesnakes molt exactly ████ █ █████
The author doesn't need to assume molting happens exactly once a year. As the visual illustrates, the method works at any consistent rate. If, for example, rattlesnakes molt twice a year, you'd divide the section count by two to get the snake's age. If they molt three times a year, you'd divide by three. The key assumption is that molting is predictable, not that it happens at the specific frequency of 1 per year.
b
The rattles of ████████████ ██ █████████ ███████ ███ █████████ ██ ███████████
The overall appearance of different rattles doesn't matter. The author's method is about counting sections within a single rattle, not comparing rattles across species. Whether the rattles of different species look the same or different has no bearing on whether you can infer a particular snake's age from its own section count.
c
Rattlesnakes molt more ██████████ ████ █████ ████ ████ ████
The frequency of molting doesn’t matter, as long as that frequency is predictable. Maybe rattlesnakes molt once a month throughout their entire lives. We could still infer a snake’s age by counting the number of sections in its rattle.
d
The brittleness of █ █████████████ ██████ ██ ███ ██████████ ████ ███ ██████ ██ ███ █████████████ █████
The author's conclusion is a hypothetical: if rattles weren't so brittle, then we could use them to infer age. Since the conclusion already removes brittleness from consideration, the author doesn't need to assume anything about how brittleness relates to age. Whatever is true about brittleness in the real world doesn't affect what would be true in the hypothetical world where rattles don't break.
e
Rattlesnakes molt as █████ ████ ████ ██ ██████ ██ ████ ██ ████ ████ ██ ██████████
If this weren’t true, it would mean that at least one other factor besides age can influence how many sections a rattle has. And that would mean we can’t infer a snake’s age solely from the number of rattle sections. We’d also have to know how food availability has affected that number. If food scarcity could speed up or slow down molting, then two snakes of the same age could have different section counts depending on how well-fed they've been. That's exactly the "unpredictable" scenario from the visual: you'd see a section count and have no way to know whether it reflects age alone or age plus dietary history.