The main purpose of is to inform or explain.

a.) exposition
b.) narrative
c.) fiction
d.) proposition

The main purpose of exposition is to inform or explain. This is a device used commonly in television, radios, films, literature such that these awaken a lot of minds of the audience. It is the way of the writer to inform the background os something particular. Hence the answer to this problem is A. exposition

Aindependent clause should follow the dependent clause