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': 'The recommended time for prophylactic antibiotic is : \nSelect and explain. \nA. 30 min. prior to induction of anaesthesia, B. 15 min. after the initiation of surgery, C. At the time of induction, D. At the time of skin incision', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]