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'.
Q: Sentence 1: Harry met Larry at the library to study for the big test. Sentence 2: They chatted instead of studying. Sentence 3: On the day of the test they were both unprepared. Sentence 4: Harry and Larry failed their test. Sentence 5: They vowed to never make that same mistake again. Choices: a. Undecided. b. Mistake.
A:
b