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: Radiology
[{'content': 'If the right cardiac silhouette is obliterated, it means the pathology involves – \nSelect and explain. \nA. Right lower lobe, B. Right atrium, C. Right middle lobe, D. Right ventricle', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Right middle lobe lesion causes obliteration of the right cardiac border (right cardiac silhouette).', 'role': 'assistant'}]