B, it gives them a reason to care about the characters and the story.
Exposition is only background for the story, so it doesn’t resolve the story’s conflict or tells what ultimately happens to the characters, nor does it necessarily decrease tension in a story (sometimes it even increases tension).
The main purpose of exposition is to establish context and tell readers the background behind what is happening in the story as well as the backstories of characters, and good exposition will most likely give readers information that prompts them to care about the characters and the story.
