Bunuel wrote:
Hannibal chose to invade Roman territory by the northern route, crossing the Alps doing it, instead of by sea.
A. doing it, instead of
B. to do so, rather than
C. to do it, rather than coming
D. to do so, instead of invading
E. to do it, instead of invading Roman territory
Magoosh Official Explanation
Split #1: repeating a predicate. One cannot use “it” to represent the action encapsulated in a verb. The proper way to refer to such action is with the substitute phrase “do so“. Choices (A) & (C) & (E) make the mistake of using the pronoun.
Split #2: “instead of” vs. “rather than“. The “of” in “instead of” is a preposition, and its object must be a noun. Thus, “instead of” can only be used to compare single nouns, and the GMAT Sentence Correction seems to avoid even this use. The GMAT also seems to avoid the “instead of” [gerund] structure. The “than” in “rather than” is a subordinate clause, so the structure “rather than” is considerably more flexible in what can follow it. Choices (A) & (D) & (E) all use an “instead of” structure of which the GMAT would not approve.
Split #3: common words in parallel. The common words “to invade Roman territory” can be dropped. The only difference between the two branches is the proposition, “by the northern route” vs. “by sea“, so that’s all that needs to be said in the second branch. Choice (C) & (D) include more than necessary, and choice (E) is simply ridiculous in its awkward length.
The only possible answer is (B).