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
Right border of the hea in a chest X-ray is not formed by: 
Select and explain. 
A. WC, B. SVC, C. Right atrium, D. Aoa
D: Aoa
Answer: D: Aoa 
Explanation: Ans. Aoa