Answer: D. have lives and stories of their own.
Side characters in a novel tend to have lives and stories of their own. A side character or supporting character is a character not part of the main focus in a primary storyline. In novels particularly, side characters are often developed side stories of their own that may link to that of the main character in an independent way. This is made possible as a result of the large content of novels which gives room for intense explanation and very descriptive storytelling.