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: Tim started yoga to get more flexible. Sentence 2: He didn't realize which class he signed up for. Sentence 3: Tim accidentally picked the advanced one. Sentence 4: He tried stretching too hard and hurt himself. Sentence 5: He didn't return to that class. Choices: a. Over Stretching. b. Botany.

a