Best answer: focus on voice, tone, and word choice.
Taking an assessment of the voice and tone of your essay, as well as word choices, are part of the revision process.
Some of the other options listed include things that should be determined well before the revision phase. Choosing your topic is a first step in the process, based on some preliminary research. As you continue the research phase, you would be are searching through reasons, evidence, claims and counterclaims, and opinions in regard to your chosen topic. .
Matters such as proofreading, judging your word choices, checking the accuracy of your citations and bibliography list, and checking your voice, style and tone -- those are parts of the revision phase of your essay work.
