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: Tom went horseback riding. Sentence 2: It was his first time. Sentence 3: It took him several minutes to control the horse. Sentence 4: After a while he became much better. Sentence 5: Tom had a lot of fun by the end. Choices: a. Flat tire. b. Horseback.

b