Photovoltaic cells are made of two thin layers of material, one of the

Hello experts ,
I was wondering whether you could provide some assistance regarding answer choice D,
The reason I picked D , was because I thought that we care about the order of the materials whether the bottom layer is made of silicon and the upper layer of aluminum or silver, C is more concise, but it doesn't clarify the order of the layers, is there a grammatical issue that helps us to eliminate D?

Yeah, this is a tough one. First, while wordiness isn't grounds for eliminating an answer, if you had two options remaining, and one of them was clearer and more concise, it's perfectly reasonable to use that as a tie-breaker. For example, compare the following options:

1) Tim has two children, one gentle and kind, the other in prison for murdering a plate of pancakes.

2) Tim has two children, the first of the children gentle and kind, the other child in prison for murdering a plate of pancakes.

While the second sentence isn't necessarily wrong, it's clearly not as good as the first. Why write, "the first of the children" when "one" conveys the exact same information? After all, we already know from the first clause that Tim has two kids, so it's clear what "one" means, without elaborating.

You get a similar choice in this question. (C) uses "one" to refer to a layer, while (D) contains "the first of the layers." Clearly, (C) is a more efficient way of expressing the same idea.

So I don't think it's unreasonable to use this as a decision point. But if you're skeptical, there's a subtle meaning issue as well. In (C) we have the phrase, "one [a layer] of a semiconducting material such as silicon." The preposition "of" suggests that the layer is made of a semiconducting material. This is perfectly logical: you acquire some semiconducting material, such as silicon, and then you assemble it into a layer.

Contrast this with (D): "the first of the layers a semiconducting material such as silicon." Now it sounds like the layer is itself a semiconducting material, as opposed to being comprised of one.

Note that (E) has the same logical problem as (D), in addition to another issue. What is "both metals" referring to? Silver and aluminum? What about Silicon? Why would we use "both" if there are three metals mentioned? If "both" is in reference to layer 1 and layer 2, then we're back to the logical problem that the layers are not themselves metals.

In any event, (C) is more logical, and therefore better.

It's important to note: if I saw (D) or (E) first, I wouldn't be comfortable eliminating either immediately. Instead, I'd note the issues as potential problems and keep them in mind in case I need to do a side-by-side comparison. Because I see no problems with (C), and I have solid reasons to prefer this option to (D) or (E), I'd be comfortable pulling the trigger, even if I wasn't 100% certain that the other options were definitively wrong.

Your goal when evaluating an SC question isn't certainty. It's to make good, logical decisions under pressure.

I hope that helps!

GMATNinja, can you please clarify what approach we should adopt to determine that categorization as in D is not required? Ca you please explain what is the meaning error in D?

It's almost impossible to eliminate (D) in a vacuum. It's only when we compare it with (C) that we can see that (C) is more logical and more concise than (D).

Put another way: there is no good concrete error in (D), so this question is less about internalizing any grammar rule than it is about learning how to do a side-by-side comparison between two options when nothing is obviously wrong, something you'll often have to do in the toughest SC questions.

Take another look at our response above and let us know if you still have questions about why (C) is better!

GMATNinja, can you please help to clarify why D is not correct? What are the main triggers in the sentence we should focus on to eliminate D?

AjiteshArun GMATNinja
Can you kindly clarify the usage of 'being' in the GMAT SC?

Hello Metalking,

We hope this finds you well.

To answer your query, “being” is only to be used when it is part of a noun phrase or represents the passive continuous verb tense; the use of passive continuous must be justified in the context.

To understand the use of "Being" on GMAT, you may want to watch the following video (~2 minutes):



All the best!
Experts' Global Team

You're in luck! We have a whole article dedicated to "being." Check it out here.

Thank you GMATNinja

(A) one of them being a semiconducting material such as silicon,
the other a metal such as aluminum or silver

(B) one of them being a semiconducting material such as silicon,
the other being a metal like aluminum or silver

(C) one of a semiconducting material such as silicon,
the other of a metal such as aluminum or silver - correct

(D) the first of the layers a semiconducting material such as silicon,
the other layer a metal such as aluminum or silver

(E) the first silicon, a semiconducting material,
the other silver or aluminum, both metals - sentence structure error

Photovoltaic cells are made of two thin layers of material, one of them being a semiconducting material such as silicon, the other a metal such as aluminum or silver.

The key here is that we need to describe that one layer is made of X and the other is made of Y. And Not One layer is X and other is Y, because if we do this then it means that one layer is semiconducting material and other layer is a metal. The layer themselves are not a semiconducting material or a metal but they are made up of either semiconducting material or a metal.

A one of them being a semiconducting material such as silicon, the other a metal such as aluminum or silver - "one of them being a semiconducting material" wrong meaning as if the layer is a semiconducting material.

B one of them being a semiconducting material such as silicon, the other being a metal such as aluminum or silver - same as A.

C one of a semiconducting material such as silicon, the other of a metal such as aluminum or silver - it conveys one is made of a semiconducting material and the other is made of a metal. ok.

D the first of the layers a semiconducting material such as silicon, the other layer a metal such as aluminum or silver - "the first of the layers a semiconducting material " means "the first of the layers IS a semiconducting material" and the "the other layer IS a metal such as aluminum or silver ."

E the first silicon, a semiconducting material, the other silver or aluminum, both metals - same issue. It conveys the first layer is a semiconducting material and the other is silver or aluminum, both metals. Wrong.