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: Alice heard the starting gun and took off. Sentence 2: She was participating in her city's annual marathon. Sentence 3: Months of training led up to this event. Sentence 4: By the last mile, she was exhausted, but determined. Sentence 5: Alice went on to set a personal best that day. Choices: a. Marathon. b. First grade.

a