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#24 - Many homeowners regularly add commercial fertilizers

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Complete Question Explanation

Must Be True. The correct answer choice is (C)

This stimulus presents information about the nutrients required for lawns to remain healthy. Many homeowners regularly add commercial fertilizers to their lawns and gardens, so that they can maintain a healthy balance of nutrients in the soil. However, it appears that using these commercial fertilizers isn’t enough. The widely available commercial fertilizers contain only macronutrients, namely nitrogen, phosphorus, and potassium. However, to remain healthy in the long term, soil for lawns requires more than just macronutrients. It also requires trace amounts of micronutrients such as zinc, iron, and copper. The micronutrients are depleted when grass clippings are raked up rather than allowed to decay and return to the soil.

This is a Must Be True question. The correct answer to this question will contain either an inference possible from a combination of the facts presented in the stimulus, or it will contain only a restatement of one of those facts. Here, an inference from a combination of the facts is possible. As described above, since the widely available commercial fertilizers do not contain trace amounts of micronutrients, then using only these fertilizers is not enough to maintain a healthy lawn over the long term. Some source of the listed micronutrients must be used in addition to the commercial fertilizer.

Answer choice (A): The stimulus said only that the widely available commercial fertilizers do not contain trace amounts of certain micronutrients. This fact does not preclude the possibility that some single fertilizer, though not a widely available, commercial fertilizer, contains both the macronutrients and micronutrients necessary for maintaining soil’s long-term health.

Answer choice (B): This answer choice is incorrect, because it is a reversal of the information in the stimulus. The facts in the stimulus were that the widely available commercial fertilizers contain only macronutrients. It did not say that the macronutrients are available only in commercial fertilizers.

Answer choice (C): This is the correct answer choice. As described above, the stimulus stated that for a lawn to remain healthy long term, both certain macronutrients and trace amounts of certain micronutrients are required. The widely available commercial fertilizers do not contain the micronutrient trace amounts, and raking up grass clipping prevents the clippings from returning the micronutrients to the soil. So, the widely available commercial fertilizers are not sufficient to maintain a healthy balance of nutrients in soil for lawns where grass clippings are not allowed to decay and return to the soil.

Answer choice (D): The stimulus did not identify commercial fertilizers as the only source of the required macronutrients. Thus, it is not supported to say that commercial fertilizers are required for soil to remain healthy in the long term. Rather, it is providing a regular source of the listed macronutrients and trace amounts of the listed micronutrients.

Answer choice (E): Similarly to the issue of macronutrients and commercial fertilizer in answer choice (D), the stimulus did not establish that grass clippings are the only source of the trace amounts of micronutrients required for having a healthy lawn in the long term.
lsatqueen
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Please help; why is the answer C and not D? I am very confused as to why this is incorrect, namely because it seems that the wording of D mirrors exactly what the stimulus says.
Adam Tyson
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Careful there, Your Highness - does answer D really mirror the stimulus? Far be it from me to disagree with your royal personage, but if you would indulge me I will try to explain my humble self. ;-)

The stimulus says that healthy soil need both macro- and micronutrients. It also tells us that commercial fertilizers have those macronutrients and that grass clippings have the micro ones. But does it say that healthy soil needs commercial fertilizers? No, my liege, it does not!

Here's a quick analogy for you: I need chocolate in order to stay happy, and M&Ms have chocolate in them. Do I need M&Ms to stay happy? Nope - they might help, but so might a Hershey bar or a brownie or some chocolate ice cream. It's not the M&Ms that I need but the chocolate found in them, much like soil doesn't need commercial fertilizers but rather the macronutrients found in them.

By your leave, Highness, and may it please you greatly. All hail to the Queen!
Adam M. Tyson
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avengingangel
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Thanks for the explanation. I agree that D is wrong, but with C is still confusing because the stimulus says that macronutrients are used "to maintain a healthy balance of nutrients in soil." The argument then proceeds to make a distinction, and notes that additionally trace amounts of micros are needed for long-term health. But answer choice C is not talking about what's sufficient for long-term health, it's just trying to maintain the healthy balance!!!
Adam Tyson
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I think you might be looking at a distinction without a difference there, avengingangel. The author tells us that the commercial fertilizers have only one kind of nutrient, and soil needs another kind as well in order to stay healthy. That's enough for us to conclude that the commercial fertilizers do not provide a "healthy balance", because they are unbalanced, missing something essential to long term health. Don't get too picky about them using different terms here! And if micronutrients are required for long term health, doesn't that indicate that their absence is unhealthy? Your analysis depends on their existing some status that could be called a "healthy balance" in the short term that does NOT lead to good health in the long term. I wouldn't call that a healthy balance - I would call that a problem waiting to happen!
Adam M. Tyson
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LSAT2018
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Administrator wrote:
Answer choice (C): This is the correct answer choice. As described above, the stimulus stated that for a lawn to remain healthy long term, both certain macronutrients and trace amounts of certain micronutrients are required. The widely available commercial fertilizers do not contain the micronutrient trace amounts, and raking up grass clipping prevents the clippings from returning the micronutrients to the soil. So, the widely available commercial fertilizers are not sufficient to maintain a healthy balance of nutrients in soil for lawns where grass clippings are not allowed to decay and return to the soil.


So the answer choice is a contrapositive of the statements?
Healthy in the Long Term → Macronutrients and Micronutrients
No Macronutrients or No Micronutrients → Not Healthy in the Long Term

So when it says widely available commercial fertilizers are not sufficient, it means they will not maintain a healthy balance?

Ps. Wouldn't the phrase 'in the long term' be needed here?