B.It allows authors to change the pace of a story.
Explanation:
The subplot is a secondary plot that supports the main plot. The pace of the story is the speed if telling a story.
The subplot can develop the story in a different direction. It can include some other parts of the theme and story, some other aspects of characters and another story that is connected to main characters.
This another story about characters that can change the pace of a story. It can slow the pace because the subplot will bring new details or change the perspective of the character. The pace of the story can be also fast when in subplot is included a part that can explain some actions and behavings of characters.
