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: Mark was a big fan of nature. Sentence2: He decided to bring trees to the city. Sentence3: He would take a truck load of trees down each week. Sentence4: He would then plant the trees in parks. Sentence5: Over time the trees grew and now Mark is happy!

SOLUTION: Mark

PROBLEM: Sentence1: Zack was always worried about getting sick. Sentence2: And he became so worried about the air that he wore a respirator. Sentence3: He wore it during his entire school day. Sentence4: And he told other students that the air quality was terrible. Sentence5: Zack still ended up getting sick and worried much more.

SOLUTION: Other students, Zack

PROBLEM: Sentence1: I had a bad rash on my arm. Sentence2: The pain was really bad. Sentence3: I ran water over it to stop the pain. Sentence4: The water did nothing to end the sharp pain. Sentence5: Finally, I used lotion and that made me feel much better.

SOLUTION:
I (myself)