Answer: Freewriting.
The other answerer is wrong. Outlining isn't brainstorming, it's just organizing.
I included a screenshot from my schoolwork that proves that this answer is correct.
More proof, an excerpt from my school lesson about <u>compare and contrast</u> topic ideas (i underlined the important parts):
<em>If you are not sure what to write about, or if you have not been given a specific topic, t</em><u><em>here are a couple of ways to generate topic ideas: freewriting and listing.</em></u>
<em>Freewrite for a few minutes. When freewriting, you should write without stopping to think or edit—just write about whatever comes to mind.</em>