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: Anatomy
[{'content': 'Only nerve that originates from the dorsal surface of the brain stem is \nSelect and explain. \nA. Trochlear, B. Occulomotor, C. Vagus, D. Abducent', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]