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': 'Which one of the following is the shortest acting intravenous analgesic – \nSelect and explain. \nA. Remifantanil, B. Fentanyl, C. Alfentanil, D. Sufentanil', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Remifentanil is the shortest acting opioid due to rapid hydrolysis by pseudocholinesterase.', 'role': 'assistant'}]