PrepTest 124, Section 1, Question 15
Earthworms, vital to the health of soil, prefer(42 more words not shown)
Which one of the following(8 more words not shown)
- AAs far as(18 more words not shown)
- BAfter its application(22 more words not shown)
- CCrushed limestone contains(16 more words not shown)
- DBy itself, acidity(10 more words not shown)
- EAlkaline soil is(15 more words not shown)
Reading the argument
What if we fix the acidity problem by creating the opposite problem?
Earthworms prefer soil near the middle of the acid-to-alkaline scale. The top layer is highly acidic, and crushed limestone is highly alkaline. Adding limestone could move the soil toward the middle, which makes the plan sound reasonable.
But suppose we add enough to push the soil too far in the other direction. It would then be strongly alkaline rather than roughly neutral. We wouldn't necessarily have made it more attractive to earthworms. My first concern is whether the treatment overcorrects.
What we’re looking for
This is a necessary-assumption question. I'd expect an answer excluding that problem: the limestone won't push the soil too far past the neutral range. Keep the actual conclusion in mind, though. We are trying to make the soil attractive to earthworms, not prove everything about how earthworms improve soil.
Working the answers
- A
We don't need to rank the jobs earthworms perform. Even if helping dead plants decompose were a minor function, the argument could still claim that treating acidic soil would attract earthworms. Their most important contribution to soil health isn't the missing link in that claim.
- BCorrect
This identifies another requirement before we even reach the overcorrection concern: the limestone has to stay long enough to neutralize some acidity.
What if it leaves the top layer before doing that work? Then putting it on the surface wouldn't make that layer less acidic through the proposed process. The argument relies on the limestone having time to produce the change that is supposed to attract the worms.
B doesn't guarantee success or settle how much limestone to use. It names something the proposed explanation needs to be true. That is enough for a necessary assumption, even though it isn't the particular requirement we first predicted.
- C
Calcium and magnesium might have benefits, but this argument doesn't depend on them. Its proposed connection is that alkaline limestone reduces excessive acidity, making the soil closer to what earthworms prefer. Mineral content and its separate contribution to soil health are not required for that reasoning.
- D
The passage says decomposing plants makes soil acidic. It doesn't need to establish whether acidity also speeds up decomposition. Those are different directions of influence. The plan relies on reducing existing acidity, not on denying every possible effect acidity might have on dead plants.
- E
This compares how much different soils benefit from more earthworms. Our question is whether earthworms would find the treated soil more attractive. A soil's need for the worms' help doesn't establish that the worms want to live there. E addresses the benefit after attracting them, not whether the proposed treatment will attract them.
More Necessary Assumption questions
Learn the LSAT our way
Our platform drills Necessary Assumption questions at your level and adjusts as you improve.