PrepTest 111

Incorrect. While something about rats makes them not produce symptoms of the disease while other animals do, we don't know that's because of their physiology. And even if it is, it might be a minor difference, not a radical one.

Incorrect. While the rats didn't develop symptoms, that may not because they failed to eat enough of the plant—they could be immune to the disease for some reason.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
Lathyrism is:
(1) A disease caused by a plant
(2) Widespread in some countries in domestic animals
(3) Has recognizable symptoms (we know this since the rats are said to not produce those symptoms, so it must produce symptoms that can be seen in other animals)
Trying to study it in rats failed because they didn't have those symptoms.

Answer Anticipation:
Don't get tripped up by the language here—it's just talking about a disease, a plant, and some animals.

It's hard to anticipate what, exactly, the correct answer here will state, but there are a couple notable elements we can focus on. First is the causality—the disease is caused by a legume. Second is the comparison—some domestic animals show symptoms of the disease, but rats don't.

With those two details in mind, let's head to the answers.

Answer Explanation:
Domestic animals develop symptoms when they have lathyrism, but lab rats don't, so the stimulus provides an example of at least one species that is less susceptible to lathyrism than domestic ones. This answer is therefore supported by the stimulus.

Key Takeaway:
When you can't anticipate a specific answer in a Must Be True question, identify statements that are likely to play into the correct answer—strong statements, comparisons, causal relationships being the primary ones.

Incorrect. It's established that lathyrism is widespread among domestic animals in some countries, but it could be even more widespread among all wild animals except rats worldwide.

Incorrect. We only know that lab rats don't lead to the development of symptoms—it could be that other lab animals do develop symptoms.