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: Erin and her sister were born several years apart. Sentence 2: Mary was just the baby, to grown up Erin. Sentence 3: They were always fighting and arguing with one another. Sentence 4: As they got older they started to enjoy each other's company. Sentence 5: Now they are adults that have become as close as two people can be. Choices: a. Baby Sister. b. California Dreaming.
a