LSAT Question Explanation
PT 108, Section 2, Question 5
Necessary AssumptionArgument structure
The cows will probably learn to graze on the grass that doesn't have the harmful fungus in it.
Cows avoid eating grass if they sense that it contains a substance that has made them sick in the past.
Explanation
The author concludes that the cows will avoid the contaminated grass because cows avoid grass when they can sense harmful substances in it. But we have no idea if they can sense the fungus.
This argument is flawed, because the author is just assuming that the cows will be able to somehow sense the fungus that made them sick.
Answer choices
We don't care whether or not there's some other fungus in some of the grass. The author is just saying the cows will learn to avoid the grass with the harmful fungus from the stimulus.
This is needed for the conclusion to hold. We need to know that the cows can sense the fungus, or else they may not avoid eating the contaminated grass.
This doesn't have to be true. The argument is just saying that the cows will learn to avoid the grass on Smith's land that has the fungus. We don't care if the fungus exists somewhere else, or in some other type of grass.
We don't need to know this, the conclusion is just that the cows will learn not to eat the contaminated grass. We don't care if other animals get sick from the fungus.
It doesn't matter if the fungus can be eradicated while leaving the grass intact. The conclusion is just about if the cows will learn not to eat the contaminated grass.