This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Radiology
Identity the structure in the given chest X-ray: 
Select and explain. 
A. Left-Costophrenic angle, B. Left-Cardiophrenic angle, C. Right-Costophrenic angle, D. Right-Cardiophrenic angle
B: Left-Cardiophrenic angle
Answer: B: Left-Cardiophrenic angle 
Explanation: Ans. b. Left-Cardiophrenic angle