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: Randy and his son were down by the river. Sentence 2: Randy was throwing stones out onto the river skipping them. Sentence 3: His son came up to him and asked him how to do it. Sentence 4: Randy told him everything he knew and taught him. Sentence 5: Soon Randy and his son were both skipping stones on the river. Choices: a. Skipping Stones. b. Missing Sandwich.

a