Definition: In this task, you're given five sentences, numbered 1 through 5, and two options a and b for possible titles for the story. Your job is to choose the title that better fits the story. Indicate your choice by 'a' or 'b'.
Input: Sentence 1: My niece went to see the principal of her daughter's high school. Sentence 2: Her daughter had compplained of bullying. Sentence 3: My daughter had a retired schoolteacher volunteer to help my niece. Sentence 4: At the meeting everybody denied bullying and there was no proof. Sentence 5: My niece was angry and felt the volunteer did not do enough for her. Choices: a. Challenge. b. Volunteer.

b