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: Susan loved to work crossword puzzles. Sentence 2: She bought books of them and carried one everywhere. Sentence 3: One day at lunch a coworker asked her about the puzzle she was doing. Sentence 4: The coworker loved to work crosswords, too! Sentence 5: Susan and the coworker became good friends. Choices: a. Expensive watermelon.. b. Puzzle Friends.

b