Though the Pythagorean theorem is attributed to Pythagoras,

Though the Pythagorean theorem is attributed to Pythagoras, a mathematician and philosopher who lived in the 6th century BC, the first proof had not been completed before the year 300 BC, when it appeared in Euclid’s Elements.

Pay attention to the last part of the sentence: it' s a modifier. "when it appeared in Euclid’s Elements" what should modify? The proof that appeared in Euclid's Elements.
So in the underlined part we must have the "proof" (otherwise that modifier makes no sense)

B. it had not been proven to be true before the year
E. it was not proven to be true prior to

Out B and E that do not have "proof". We are left with A C and D.

A. the first proof had not been completed before the year
The past perfect must express an action that happened for a long period of time,this is not the case. Out A
C. the first proof of the theorem was not completed prior to
D. the first proof was not completed until

Between C and D, D is the better chioce. D is more coincise (clearly) and C uses "prior to" (not an error by itself, but "until" is preferred)

hi ,
even myself also chose D after eliminating A B E.
You mean to say if in option C we have until instead of prior to then also option D is correct because it is concise.
but as per my understanding option C's wording is more clear: the first proof of the theorem rather in option D Proof of what? it is not clear.

please suggest if i am wrong.

SKM
also until is prefered over prior to ===> is that GMAT preference you mean.

I do not remeber a single Offical Example in which "prior to" is used. As I said before, I cannot say that it's wrong by itself, but "until" is preferred

And yes, "proof of the theorem" would make the sentence more clear in my opinion. What is the source?

Hi ratinarace, answer choice B changes the meaning and doesn't work with the rest of the sentence. The proof of the Pythagorean theorem is what appeared in Euclid's work, not the theorem itself. The unclear pronoun "it" seems to be referring back to the theorem itself, not the proof. As such, it is incorrect (as is E which also uses the pronoun "it").

As for D vs C, I saw it more as a subtle difference in meaning. "The choices are really:

C. the first proof (..) was not completed prior to
D. the first proof was not completed until

Between these two, the meaning of D is correct, it was not proven correct until 300 AD, when it was published. That's when it was proven. Answer choice C lacks a clear connection between the two. It was not completed before... some arbitrary timeframe... for example not completed prior to the fall of Rome (476 AD but let's just assume 476 BC for the sake of this question).

Was not completed prior to the fall of Rome --) timeframe with no causality
Was not completed until the fall of Rome --) timeframe with causality, this was completed at exactly that point.

Therefore the extra words in C do clarify the issue a little, but they don't matter compared to the meaning discrepancy between the two choices.

Hope this helps!
-Ron
_________________

Thanks Ron! You're in fact one of the best out here. But let me tell ya something. How can a proof be completed? It should be the theorem that is completed not the proof. I'm smelling a meaning error over hear

Please clarify
Thanks!!
Cheers
J

Hi ratinarace,


If you closely look into the sentence given, it is stated that the 'the first proof was not completed until' blah blah..

So you can infer that there were multiple proofs for the same theorem..

So to answer 'how can a proof be completed?'

How can you start a second proof unless or until the first proof is completed?

And I guess every valid theorem has a proof, which needs to be completed.
I hope i made myself clear

avigutman not cler on the causality difference cited here
Which causality is there in until and not in prior to

I don't get why "when it appeared in Euclid’s Elements." modifier can't modify the theorem but only the proof?