This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular Radiology, Subject name: Radiology
[{'content': 'Angle of tracheal bifurcation is increased in which chamber of hea enlargement. \nSelect and explain. \nA. Left atrium, B. Right atrium, C. Left ventricle, D. Right ventricle', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Normal tracheal angle: 40- 80deg The angle of tracheal bifurcation may be widened in the following conditions due to the mechanical splaying of the bronchi: Subcarinal masses Lobar collapse Left atrial enlargement Generalized cardiomegaly Pericardial effusion', 'role': 'assistant'}]