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
A triangular opacity with clear borders, base towards midline and obliterating right heart border on a chest radiograph suggest that the pathology is likely to be in - 
Select and explain. 
A. Apical segment of right lower lobe, B. Medial segment of right lower lobe, C. Right middle lobe, D. Any of the above
C: Right middle lobe
Answer: C: Right middle lobe 
Explanation: Right middle lobe pathology obliterates lower right border of heart producing silhouette sign.