Question

which of the following is a common purpose of literary authors?
to persuade a government to change a law
to teach a specific school subject
to explain a process for doing something
to express a message (theme) about human nature

Explanation:

Literary authors often create works to convey themes or messages about human nature, emotions, or experiences. Persuading governments to change laws is more of an activist or political writer's goal, teaching a school subject is for educational materials, and explaining a process is for technical or instructional writing. So the common purpose of literary authors here is to express a message (theme) about human nature.

Answer:

to express a message (theme) about human nature