Logical reasoning PrepTest 144 · Section 3 · Question 24

Incorrect. The widely available commercial fertilizers don't contain the micronutrients, but there may be a fertilizer that's not widely available or not commercial that does.

Incorrect. These macronutrients (and others) are the only things in the widely available commercial fertilizers, but they could very well be available through other means—it never establishes that these fertilizers are the only source of them, just that these fertilizers contain only these macronutrients.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
Goal Ð Healthy nutrient balance in soil
Approach Ð Add commercial fertilizers to lawn
Widely available commercial fertilizer contain only macronutrients
Long-term healthy lawn soil → Macronutrients AND Micronutrients
Grass clippings raked up (not allowed to decay) → Micronutrients depleted

Answer Anticipation:
There's a decent amount going on in this stimulus, but there's one statement that is key. That statement establishes what is necessary to maintain a healthy lawn over time. We know this statement is key for three reasons:

(1) It addresses what is required to meet the goal set out in the first statement
(2) It's a conditional rule
(3) It connects to all the other premises

That last one is particularly important, as the more premises we can connect, the more likely we are to anticipate the correct answer.

So the goal is to maintain a healthy lawn, which requires a mix of micro- and macronutrients. The fertilizers provide the latter, but the former are depleted when grass clippings are raked up and tossed instead of allowed to decay back into the soil.

Bringing this all together, we can see that the soil won't be healthy if the grass clippings are allowed to decay without the fertilizer (or some other source of macronutrients), or if the fertilizer is added but the grass clippings are raked up (and the micronutrients thus lost aren't replaced by some other method). That's a lot of moving pieces, so let's leave ourselves plenty of time to analyze the answers and head down to them ASAP!

Answer Explanation:
Where grass clippings are not allowed to decay, micronutrients are depleted. Micronutrients are necessary for a healthy lawn, long-term. The widely available commercial fertilizers don't contain micronutrients (they contain only macronutrients). So since the widely available commercial fertilizers don't contain something that is necessary for a healthy lawn, they're not by themselves sufficient to ensure a healthy soil balance in a lawn where those micronutrients are being depleted when grass clippings aren't allowed to decay back into the soil.

Key Takeaway:
When two terms talk about the same concept, there's a good chance an inference can be drawn from them. When a statement shares terms with most other statements in a stimulus of a Must Be True, it's probably a good idea to start there to start putting all the pieces together.

Incorrect. First, the stimulus is about soil for lawns, and this answer is about soil generally, which is a shift that invalidates the answer. Additionally, the stimulus establishes only that macro- and micronutrients are both necessary for a healthy soil nutrient balance. It doesn't establish that these nutrients need to be "regularly added," just that they need to be present. It's possible that the macronutrients aren't depleted much after they're present, and so any addition of them doesn't need to be regular.

Incorrect. While these homeowners are removing necessary micronutrients from the soil, there's no indication that they can't replace them with some other type of fertilizer.