You will be given a definition of a task first, then some input of the task.
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: Sandy Beach. Sentence 1: Brent and his friends went to the Beach and played in the sand. Sentence 2: When Brent arrived back home, he tracked sand into the house. Sentence 3: His wife screamed and cried because of the mess he made. Sentence 4: Brent cleaned up the sand and promised not to make a mess again. Choices: a. Brent learned to clean up after his own messes. b. Knocks on the door but no answer!
Output:
a