Answer: A) Show's.
Explanation: a pronoun is a word that can function as a noun phrase used by itself and that refers either to the participants in the discourse or to someone or something mentioned elsewhere in the discourse. The antecedent of a pronoun is the word or group of words that precedes the pronoun. In the given sentence, the antecedent of the pronoun "its" is "show's" because it is saying that the show's appeal to teenagers is what explains its success.