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
The following will be most helpful radiological investigation in a patient suspected of left pleural effusion 
Select and explain. 
A. Right lateral decubitus, B. Left lateral decubitus, C. Left lateral erect, D. Right lateral erect
B: Left lateral decubitus
Answer: B: Left lateral decubitus 
Explanation: B i.e. Left lateral decubitus