Teacher: 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.
Teacher: Now, understand the problem? If you are still confused, see the following example:
Sentence1: My dog was bored. Sentence2: I was working all day so I couldn't spend time with him. Sentence3: When I finished work I decided to play with my dog. Sentence4: He was so happy to finally have some fun! Sentence5: Alas, he fell sick and died.
Solution: I (myself), Dog
Reason: There is only two characters in given story, i.e., I (myself) and dog.

Now, solve this instance: Sentence1: Sierra was playing with her cat in the living room. Sentence2: She was petting the cat's fur when she noticed some little black dots. Sentence3: Upon closer inspection she realized her cat had fleas. Sentence4: She made an appointment with the vet right then. Sentence5: The bugs cleared up quickly with some medication.
Student:
Sierra, Fleas, Vet, Cat