I received a PM asking me to reply. (Sorry it has taken me so long. I'm getting ready to move from one country to another, so things are a bit crazy right now! Also, FYI, I won't be able to respond to any PMs / answer any more questions until around the second week in January.)
On the "x rather than y" bit, it is parallel in both choices: "to quit rather than (to) wait." The second "to" does not need to be repeated and so it should not be repeated.
Generally, we stay in the same tense unless we have a reason to change tenses. In this case, though, I don't think you'd ever see the real test present a problem in this way, because "chose" (option B) is fine as well in terms of both grammar and meaning. They'd have had to give you present perfect in the original sentence as well, to indicate that this was the meaning they wanted. I've never seen them test "stay in the same tense unless you have reason to change" in this way (with two choices that are completely correct in terms of both grammar and meaning).
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Stacey Koprince
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