This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthesia, Subject name: Pharmacology
[{'content': 'Patient undergoing surgery was given a muscle relaxant. It produced marked fall in B.P. and increase in airway resistance which were reversed with diphenhydramine. The muscle relaxant was most probably: \nSelect and explain. \nA. Pancuronium, B. Diazepam, C. Tubocurarine, D. Vecuronium', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Hypotension and bronchoconstriction (increase in airway resistance) are impoant adverse effects caused by histamine. This is confirmed to be due to histamine because of reversal with diphenhydramine. * Maximum histamine release is caused by d-tubocurarine. * Vecuronium does not cause histamine release, therefore is preferred agent in asthmatic patients.', 'role': 'assistant'}]