Given the task definition and input, reply with output. 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: Root Beer. Sentence 1: My sister in-law turned 63 yesterday. Sentence 2: We had her over for cake. Sentence 3: We gave her a hard root beer. Sentence 4: After a half an hour she got itchy. Choices: a. I hope she did not have an allergic reaction. b. They won the final match 5-1.
a