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: ENT
[{'content': 'Which of the following structures is not seen on bronchoscopy - \nSelect and explain. \nA. Trachea, B. Vocal cords, C. Subcarinal lymph nodes, D. First segmental division of bronchi', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]