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: Write Your Congressman. Sentence 1: Mark wrote a letter to his congressman. Sentence 2: Mark was critical of his stance on gun control legislation. Sentence 3: Mark received a letter back from the congressman's office. Sentence 4: It was an impersonal form letter. Choices: a. Thomas opted to buy some earplugs instead. b. Mark was disappointed with his congressman.
b