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': 'A triangular opacity with clear borders, base towards midline and obliterating right hea border on a chest radiograph suggest that the pathology is likely to be in? \nSelect and explain. \nA. Apical segment of right lower lobe, B. Medial segment of right lower lobe, C. Right middle lobe, D. Any of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Right middle lobe', 'role': 'assistant'}]