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: Set a pace. Sentence 1: Bobby was running in a 5k for the first time. Sentence 2: He hadn't formally trained but he was pretty athletic. Sentence 3: After he started running he paced himself with another runner. Sentence 4: He kept up with him the whole race. Choices: a. She asked him where that skank whore was and he looked confused. b. They crossed the line together and Bobby was first in his age group.
b