ratinarace
whats wrong with B??
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