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: Anaesthesia
[{'content': 'The following are used for treatment of postoperative nausea and vomiting following squint surgery in children except – \nSelect and explain. \nA. Ketamine, B. Ondansetron, C. Propofol, D. Dexamethasone', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]