Answer:
B. They provide detail about where they are.
Step-by-step explanation:
It is said that prepoition is a word or a group of words used before a noun, pronoun, or noun phrase to show direction, time, place, location, spatial relationships, or to introduce an object. This would most likely mean that it would be used to show specifically where they are in that moment within a story.
If I am wrong, please correct me if needed