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: Dan and his wife went to an office party. Sentence 2: At the party, Dan noticed someone waving at him from across the room. Sentence 3: Dan waved back, but noticed the person kept waving. Sentence 4: Dan called out to the person, saying hello. Sentence 5: To Dan's horror, he realized they were waving at someone behind him. Choices: a. Faux Pas. b. Trouble.

a