Hello there!
Prewriting is the first stage of the writing process, typically followed by drafting, revision, editing and publishing. It is where you find an idea for a project and write it down.
There are several steps that you need to follow up when prewriting. Synthesizing information is one of those. For that proccess, you can take notes, write them down, posing research questions and start your research. Once you finish it, you can go to a new step: outlining. The organisation of your text and the structure that it must follow it's called outline, and it must be done once you have all the required information.
Therefore, outlining is the correct answer.
Hope this helps.