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: Chris found a box of caterpillars. Sentence 2: His mom thought they were gross and asked him to throw them away. Sentence 3: He want to throw them away but thought they were cute. Sentence 4: Chris decided to keep one. Sentence 5: It eventually turned into a butterfly and flew away. Choices: a. Saving Mom. b. The Pet Caterpillars.
b