The characteristic that is true of a theme is:
A. It is explained by the author.
A theme represents the underlying message or central idea of a literary work, and while it may not always be explicitly stated by the author, it is often explored and can be inferred through the characters, plot, and setting. It reflects the author's insights and viewpoints, making it a critical element of literature. However, it is not always presented in a straightforward manner; rather, it can be woven subtly throughout the narrative.