Audience!
"A" has to do with audience. Who are you planning to address? What do they think or feel about your topic? Figuring out who audience helps writers attune to the readers state of mind. It means figuring out the audience's thoughts, feelings, prejudices, attitudes, anxieties, or dreams. The better you "suss out" your audience, the more strategic you can be about using rhetorical appeals: pathos, logos, and ethos. If you know what readers think or feel, you'll know just what kind of emotions to nurture, what kind of reasoning to use, and what you'll need to do to gain their trust.