Given the task definition and input, reply with output. 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'.

Sentence 1: Jane ran down the hill really fast. Sentence 2: She fell on her way down the hill. Sentence 3: Jane hit a trash can on her way tumbling down. Sentence 4: Jane injured herself going down the hill. Sentence 5: Jane spent a week in the hospital because of her injuries. Choices: a. Riding a bike. b. Falling Down Hill.
b