Which of the following represents the first step in planning a piece of writing?
a. make an outline.
b. edit and make revisions.
c. decide on a topic.
d. consider your audience.

Hi, I guess the answer would be "deciding on a topic". It is really important that you like the topic, because you will be writing about it who knows for how long. So it would be better for you to like it, because it will make everything easier for you. "Considering your audience" can be important, but not to everybody. There are writers who write for themselves, write about the things they like, and they are not trying to ingratiate to the audience. I think that is individual, if you are scared of what the audience is going to say, then maybe this is the first step. After you decide on a topic, you are going to "make an outline" and when you finish writing, you will "edit and make revisions".