This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anaesthesia
[{'content': "In Bier's block aesthetic agent given by which route? \nSelect and explain. \nA. Intravenous, B. Peribulbar region, C. Retrobulbar area, D. Dermal", 'role': 'user'}, {'content': "Answer: A \nExplanation: (Refer: Morgan and Mikhail's Clinical Anaesthesiology, 5th edition, pg no.1000)", 'role': 'assistant'}]