This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Radiology
Luftsichel sign on chest radiograph is indicative of 
Select and explain. 
A. RUL collapse, B. Combined RLL and RML collapse, C. LUL collapse, D. LLL collapse
C: LUL collapse
Answer: C: LUL collapse 
Explanation: .