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
Lt border of the hea in C.X.R. is formed by: 
Select and explain. 
A. Pul.aery, B. Pul. vein, C. Abdominal aoa, D. All
A: Pul.aery
Answer: A: Pul.aery 
Explanation: A i.e. Pulmonary aery