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: What cost?. Sentence 1: Cortana had a severe sleeping problem, she hadn't slept in days. Sentence 2: The doctor prescribed to her some sleeping pills but they didn't work. Sentence 3: The next thing that was recommended to her was an ancient tea. Sentence 4: It was Chinese and it cured her insomnia and she was able to rest. Choices: a. The only side effect was that she was haunted by the worst nightmares. b. They got their doughnuts and ate, they were amazing Jasmine thought.
a