TASK DEFINITION: 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.
PROBLEM: Sentence1: Jennifer wanted to organize her living room. Sentence2: She bought a tall bookshelf to contain the clutter. Sentence3: She put some cute knick knacks on it as well. Sentence4: Jennifer felt like her living room was really coming together. Sentence5: She liked having a clean, organized space!

SOLUTION: Jennifer

PROBLEM: Sentence1: Martha sat quietly on the subway as she waited for her stop. Sentence2: An elderly woman boarded the train and held onto the subway rail. Sentence3: Martha felt bad. Sentence4: She stood up and offered her seat to the elderly woman. Sentence5: The woman thanked Martha enthusiastically.

SOLUTION: Woman, Martha, Elderly woman

PROBLEM: Sentence1: Jim went to play ultimate Frisbee with his girlfriend. Sentence2: They tossed a disc around for hours at the park. Sentence3: Finally they formed a team with some people at the park. Sentence4: They played for hours. Sentence5: Jim and his girlfriend were completely drenched in sweat afterwards.

SOLUTION:
Some people at the park, Jim, His girlfriend