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: Fred just started middle school. Sentence 2: And after each class, he received more and more books to carry. Sentence 3: He took his backpack off to fill it with books and materials. Sentence 4: And he struggled to pick it up. Sentence 5: When he put it on, he fell on his back. Choices: a. Spider. b. Heavy Backpack.

b