This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CT SCAN, Subject name: Radiology
Which of the following modality is most sensitive investigation for pneumothorax? 
Select and explain. 
A. USG, B. CT, C. X-ray, D. MRI
B: CT
Answer: B: CT 
Explanation: Pneumothorax: Refers to the presence of gas (air) in the pleural space. When this collection of gas is constantly enlarging with resulting compression of mediastinal structures, it can be life-threatening and is known as a tension pneumothorax. Provided lung windows are examined, a pneumothorax is very easily identified on CT, and should pose essentially no diagnostic difficulty. - IOC- CT Scan - Best X-ray view- Expiratory Films