Dear
avohdenI'm happy to help with this.

This question gets into several issues of Rhetorical Construction, one of the eight major areas tested on the GMAT SC. Here's an article about this topic:
https://magoosh.com/gmat/2013/rhetorical ... orrection/Here's my analysis.
(A) The Antietam campaign of 1862 was the occasion for two attempts of the Confederate army to destroy the Monocacy Aqueduct but soldiers were unable to drill enough holes into the hard stone to place explosives that would breach the aqueduct.
Notice that this is longer than all the other answers --- not definitive in and of itself, but an important clue. The construction "
was the occasion of two attempts" is a flaccid, droopy construction, about as forceful as a wet noodle. Among other things, making the word "attempt" a noun turns some of the most important action in the sentence into noun-form, which makes the whole sentence less direct and less powerful. sSe
https://magoosh.com/gmat/2013/active-verbs-on-the-gmat/While this version is grammatically correct, it's very awkward, wordy, and unnecessarily swollen. This can't be correct.
(B) Soldiers were twice unable to drill enough holes into the hard stone of the Monocacy Aqueduct to place enough explosives to breach it during the 1862 Antietam campaign of the Confederate army.
This version is trying to convey all the complex information in a single independent clause. The triple infinitive "
unable to drill ... to place ... to breach" is grammatically & idiomatically correct but awkward. If we have so much action going on that we need three infinitives, then there's a good chance we could put some of that action into another clause, either another independent clause or a subordinate clause. Also, the relationship of the soldiers and the "
Confederate army" is unclear. Also, we lost the verb "
destroy" --- yes, it's implied by the verb "
breach", but we lose the clear statement about the soldier's intentions. We can't out and out say that this answer is wrong yet: it is very poor, but if everything else were definitively wrong, we might have to settle for this.
(C) The Confederate army twice attempted to destroy the Monocacy Aqueduct during the 1862 Antietam campaign but soldiers were unable to drill enough holes into the hard stone to place enough explosives to breach the aqueduct.
This is very good. One clause for the attempt, conveying the soldier's intentions, and another clause for the result. This is a very logical sentence structure:
P attempted/intended X, but the result was Y. Everything is grammatically correct and idiomatically correct, and the sentence is clear, direct, and rhetorically strong. This is a promising choice.
(D) The hard stone of the Monocacy Aqueduct made it twice impossible to drill sufficient holes during the Confederate army's 1862 Antietam campaign for soldiers to place enough explosives to breach the aqueduct.
Hmmm. Think about the action here. If we had to choose the best subject, the best initiator of action in this situation, the "
hard stone" is not the most dynamic and potent actor. Rhetorically, this is a trainwreck. Why on earth would we make the stones the focus of the question? This is very strange and cannot be correct.
(E) The Monocacy Aqueduct was twice attempted to be breached during 1862's Antietam campaign but soldiers were unable to drill enough holes into the hard stone to place enough explosives to destroy the aqueduct.
The passive structure here is a disaster. We know who the actors are, and they are even discussed in the sentence, so having a passive structure in which the aqueduct is the focus is rhetorically unjustified. Passive structure is OK when we don't know who the subject, the doer, is, and we don't really care. Here, the doers are part of the sentence, so it's crazy to use the passive voice. See:
https://magoosh.com/gmat/2012/active-vs- ... -the-gmat/This one can't possibly be correct.
Choices
(A) &
(D) &
(E) are completely unacceptable. If we had nothing better, we could settle for
(B), but it's far less than ideal. Fortunately, we do have something better --- choice
(C) is clear, direct, powerful; it is grammatically correct, and well-organized both logically and rhetorically. It is by far the best possible answer.
Does all this make sense?
Mike