Q: In this task, you're given the title of a five-sentence story, the first four sentences, and two options for the fifth sentence as a and b. Your job is to pick the sentence option that seamlessly connects with the rest of the story, indicating your choice as 'a' or 'b'. If both sentences are plausible, pick the one that makes more sense.
Title: Cavity. Sentence 1: Tom had a really bad toothache. Sentence 2: Tom went to the dentist to get it checked out. Sentence 3: The dentist did a thorough examination. Sentence 4: Tom learned that acid from soda was ruining his tooth! Choices: a. Tom hasn't had a drop of soda since that day. b. She fell in love with him after hearing him play the guitar.
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
a