A pronoun can substitute a noun or a noun phrase. Among the options above only C. him and D. They are pronouns: stories is a noun and many could be a pronoun if is was standing alone, but here it is a part of a noun phrase.
C. him is singular, so the right answer is D. They
Side stories of other people add to the story , because it shows how they feel about the topic and sooner in the story you'll see how boo radley and tom Robinson are similar to each other
