You will be given a definition of a task first, then some input of the task.
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'.

Sentence 1: Bob heard the emergency sirens. Sentence 2: The sirens indicated a tsunami might be headed for his coastal city. Sentence 3: He was driving, so he stayed in his car and headed to higher ground. Sentence 4: He drove several miles inland. Sentence 5: Bob then heard the sirens indicating that the danger had passed. Choices: a. Tsunami Sirens. b. The Limping Dog.
Output:
a