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
Best test to detect pneumoperitoneum is: 
Select and explain. 
A. Chest X-ray, B. X-ray abdomen in supine position, C. X-ray abdomen in supine position, D. X-ray abdomen in lateral decubitus
D: X-ray abdomen in lateral decubitus
Answer: D: X-ray abdomen in lateral decubitus 
Explanation: X-ray abdomen in lateral decubitus