Given the task definition and input, reply with output. 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.

Sentence1: A class met together. Sentence2: The teacher asked for suggestions. Sentence3: One student suggested a field trip. Sentence4: The teacher agreed. Sentence5: They went to the aquarium.
Class, Student, Teacher