Q: 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: Tom was out on a hike. Sentence 2: His phone ran out of battery. Sentence 3: He liked listening to music. Sentence 4: Tom decided to buy a back up battery. Sentence 5: Tom took it next time he was hiking. Choices: a. Backup Battery. b. Tree House.
A:
a