Detailed Instructions: In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.
Q: Sentence1: Billy was excited to go to school today. Sentence2: He put on his favorite shirt. Sentence3: On the bus some girls started laughing. Sentence4: Billy realized there was a huge hole in the back of his shirt! Sentence5: Billy called his mom to bring him another one.
A:
Billy, Girls, Mom