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: The boy kicked the rock. Sentence 2: The rock came loose. Sentence 3: It fell down a hill side. Sentence 4: Someone was walking up the hill. Sentence 5: The rock almost hit them. Choices: a. rock. b. Doing the math.

a