This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Onabotulinum toxin A can be used for the treatment of: \nSelect and explain. \nA. Cervical dystonia., B. Chronic migraine., C. Blepharospasm., D. Strabismus.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Onabotilinum toxin A has recently been approved to prevent a headache in adult patients with chronic migraine.', 'role': 'assistant'}]