This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Radiology
[{'content': 'The normal carinal angle at the tracheal bifurcation is around? \nSelect and explain. \nA. 40-50 degrees, B. 50-60 degrees, C. 60-75 degrees, D. 75-90 degrees', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans CCarinal angle is influenced by indentation from adjacent structures/lesions on the tracheal bifurcation. Normally it is 60 to 75 degrees. Any mass at carina like duplication cysts or left atrial enlargement results in widening of the angle.', 'role': 'assistant'}]