# That wall is supported by several joists. The only thing that can have caused the bulge that the wall now has is a br...

on July 21 at 01:35PM

Why not D?

Can someone please explain me this question, why the answer is A and what is the problem with D?

Shunhe on July 21 at 05:32PM

Hi @Augusto,

Thanks for the question! So let’s quickly recap the stimulus. We’re told that the wall is supported by several joists (whatever those are). And the only thing that could’ve caused this bulge in the wall that’s now there is broken joist; in other words

Bulge —> Broken joist

So the argument then concludes at least one of the joists is broken. And we should take note of this: it doesn’t conclude all the joists are broken, just that there has to be at least one broken one. We’re then asked to find an argument that is most similar in logical features as the argument above; in other words, this is a parallel reasoning question.

Now let’s take a look at (A), which tells us that the conductor of an orchestra grimaced, and nothing but a player making a mistake would make the conductor grimace in that way. So, the argument concludes, at least one of the players in the orchestra must’ve made a mistake. We can see that this parallels the reasoning in the original stimulus: the only thing that could’ve caused X is Y, so at least one thing has to exhibit feature Y.

Now take a look at (D), which tells us that one of the orchestra’s players must be able to play the harp, since in one of the pieces they’re playing next week, the composer said a harp should be played. This answer choice does parallel the “at least one player” kind of logic. But remember that in the stimulus and in the correct answer choice, the reason we get to the fact that there has to be at least one thing is because of conditional logic, that only that thing could have caused whatever ended up happening. But that’s not paralleled in (D). We aren’t told that “only a harp player could play the part” or something like that, we’re just told that the composer specified that harp should be played. Well, maybe it should be, but it isn’t. Or the orchestra hired an outside harp player. It’s not the same kind of logic and not as close as (A), so (D) is wrong.

Hope this helps! Feel free to ask any other questions that you might have.