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 heart in CXR is formed by – a) Pulmonary arteryb) Superior vena cavac) Rt atriumd) Rt ventricle 
Select and explain. 
A. bc, B. c, C. ac, D. ad
A: bc
Answer: A: bc 
Explanation: None