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 does not connect with the rest of the story, indicating your choice as 'a' or 'b'. If both sentences are plausible, pick the one that makes less sense.

Title: Unwanted apps. Sentence 1: Frank installed a new game on his phone. Sentence 2: He had a lot of fun with it until it started acting up. Sentence 3: He realized that a lot of apps were being downloaded as he played. Sentence 4: He tried to remove them but it didn't work. Choices: a. And moments after the command dive was given, the sub was under water. b. He had to reboot his phone to get rid of them.
a