This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pediatrics
Obstruction in pulmonary stenosis may occur at the following sites ___________ 
Select and explain. 
A. Supravalvular, B. Valvular, C. Subvalvular, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: In PS obstruction can be supravalvular,valvular, subvalvular. Ref : Ghai essential of pediatrics eighth edition, p.no:433