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: Sword fight. Sentence 1: Felix bought a sword to put on his wall as decoration. Sentence 2: But when a thief came in his house, he took it to defend himself. Sentence 3: He threatened the thief as if he knew what he was doing. Sentence 4: The thief panicked and left. Choices: a. And Felix was relieved as he didn't know how to use a sword. b. She bought a turtle the next day.
a