Given the task definition and input, reply with output. 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: Tim was very political. Sentence 2: He decided to take part in a big protest. Sentence 3: It was cracked down on by the cops. Sentence 4: Tim was tear gassed and arrested. Sentence 5: He was proud of his efforts. Choices: a. Aluminum. b. Big Protest.
b