Official Explanation:
Both alto clarinets and alto saxophones use wooden reeds inserted in the instrument’s mouthpiece. A reed designed for one of these instruments can be used in the other, but usually some sound quality or ease of note production will be lost. However, the Unireed, a reed with a plastic cover, is specifically designed to be used with either instrument. Musicians who play both these instruments and want to save money would do well to buy these reeds.
The recommendation depends on which of the following assumptions?
(A) The sound quality produced by the use of a Unireed has improved considerably since it was first introduced.
(B) Some musicians prefer the feel of a reed with a plastic cover to one without a plastic cover.
(C) The mouthpieces for the two instruments are not interchangeable.
(D) The cost of buying Unireeds is no more than buying reeds designed for an alto clarinet or alto saxophone, regardless of the number purchased.
(E) Most listeners cannot hear the difference between instruments played with a Unireed and a standard reed.
Question Type: Assumption (‘Depends upon’ is the language that tells me this is a necessary assumption question, rather than a sufficient assumption question. The difference between sufficient and necessary assumption questions are necessary assumptions answers have ‘weaker’ assumptions with almost infinite right answers, while sufficient assumptions questions have only one right answer which tends to feature comically strong and over the top language)
Boil It Down: Clarinets and Saxophones use wooden reeds. You can interchange wooden reeds between them, but it sounds a bit worse, usually. Unireed makes plastic reeds, designed to be used with both instruments. Therefore, musicians who play both and want to save money should use Unireeds.
Goal: Find the option that shows one way the conclusion might be wrong/incomplete.
Analysis:
As we do with assumption family questions, we plug our evidence and conclusion in to help us predict the possible assumption.
Evidence:
1. Wooden reeds designed only for a Saxophone or a Clarinet sound subpar when interchanged.
2. Unireed, a company who makes plastic reeds, sells a reed which is designed to be used in either instrument.
Assumption: ?
Conclusion: If you play both these instruments and want to save money, you should buy a plastic Unireed reed.
Now that we lined the evidence and conclusion up, ask yourself: is this conclusion 100% true given the evidence? Is there any way the conclusion can be wrong? I think so. This is because the prompt is making some assumptions, and we have to figure out what those assumptions are.
For a necessary assumption question, there are lots and lots of right answers. So, when we make a prediction, don’t be discouraged if it’s not super similar to the actual answer choice.
Here, my prediction is about sound quality. The prompt tells us that wooden reeds designed for only one instrument have worse sound quality, and then introduces us to a plastic reed designed for both. Does the prompt ever explicitly say a plastic reed designed for both has better sound quality? What if it suffers from the same problems as wooden reeds? It never says any of this, so the author is necessarily assuming that a plastic reed designed for both instruments does not suffer from the same sound issues as wooden reeds designed for one or the other. I would like an answer that says something similar, but because there can be many different correct answers, I’ll ‘shop around’ to see what looks good.
(A) The sound quality produced by the use of a Unireed has improved considerably since it was first introduced.
Another classic wrong answer choice. Relative comparisons don’t prove anything. If the sound quality used to be abysmal, and now its significantly improved to only ‘slightly bad,’ should musicians still buy Unireeds? We frankly don’t care how much it has improved; we only care about whether it sounds good now. This answer choice does not tell us for certain it sounds good now.
(B) Some musicians prefer the feel of a reed with a plastic cover to one without a plastic cover.
Sure, this could be true but it's not something the author is assuming. The conclusion is that “if you want to save money you should buy a Unireed.” The author never assumes that people would think they feel the same. The author has no quarrel with musicians who would prefer to spend extra money on two reeds because they prefer the feel of wood reeds better. Rather, he’s trying to convince the more thrifty musicians to buy the Unireed.
(C) The mouthpieces for the two instruments are not interchangeable.
Do we have any indication that switching the mouthpieces matters? There is nothing in the prompt to suggest so, and my cursory understanding on musical instruments is that the reed can be taken out separately from the mouthpiece. This is a bit out of scope because we are focused on the reeds, not the mouthpiece.
(D) The cost of buying Unireeds is no more than buying reeds designed for an alto clarinet or alto saxophone, regardless of the number purchased.
This is the correct choice. Let’s plug it in to illustrate:
Evidence:
1. Wooden reeds designed only for a Saxophone or a Clarinet sound subpar when interchanged
2. Unireed, a company who makes plastic reeds, sells a reed which is designed to be used in either instrument.
Assumption: the cost of buying Unireeds is not more than buying wooden reeds, regardless of how many you buy.
Conclusion: If you play both these instruments and want to save money, you should buy a plastic Unireed reed.
This perfectly fits our conclusion that “If you want to save money, buy the plastic reeds.” The author, in concluding that plastic reeds save money, has assumed that they are the same or at least similar in price. For example, Unireeds cost $20, while wooden reeds cost 5$ each, it would be cheaper to buy two wooden reeds and the conclusion “if you want to save money…” would be incorrect. Just think of an assumption as adding an additional sentence of evidence and see if it strengthens the argument. In most cases that will help you show when something is an assumption.
(E) Most listeners cannot hear the difference between instruments played with a Unireed and a standard reed.
We don’t care about what listeners hear. I can’t tell the difference in sound quality between a $100 violin and a Stradivarius violin. Yet professional musicians still prefer the Stradivarius despite it being a magnitude more expensive. Moreover, the prompt never focuses on what listeners think, it only focuses on objective facts of whether it does or does not sound worse. This is not an assumption the prompt makes.
Don’t study for the GMAT. Train for it.