During the prewriting stage of any literature, what would you worry about? Well, you want to portray to a certain audience (Don't wanna be writing a 50 chapter horror story for a kindergarten class), so B is out of the question.
If you're writing, you obviously have a purpose to get across, it's part of the foundation of a rough draft. So there goes A.
But, if it's an essay, yes you do need to get a couple of examples. I'm going to assume that the question is regarding an essay, so C can go now.
And All that leaves is D. Now I'm not 100% sure if a medium is something you HAVE to worry about in prewriting, but I don't really worry much about it.
I'll say 'D' is the one you don't need to worry about.