This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Muscle relaxants, Subject name: Anaesthesia
[{'content': 'Which of the following muscle relaxants causes maximal pain on injection \nSelect and explain. \nA. Succinyl choline, B. Vecuronium, C. Rocuronium, D. Cistracurium', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The major disadvantage of rocuronium is the pain associated with its injection, the cause of which is not clear. With a subparalysing dose, 50-100% of patients repo discomfo.Even after induction of anaesthesia with propofol or thiopental, rocuronium causes hand or limb withdrawal in 85% of patients, suggesting the presence of intense nociception, even during anaesthesia', 'role': 'assistant'}]