This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Valvular hea diseases, Subject name: Medicine
A 5-year-old boy is referred to a pediatric cardiologist after a check-up at his GP revealed he had a murmur consistent with aoic regurgitation. What is the MOST likely cause of this defect? 
Select and explain. 
A. Atrial septal defect, B. Rheumatic fever, C. Cardiomyopathy, D. Ventricular septal defect
D: Ventricular septal defect
Answer: D: Ventricular septal defect 
Explanation: Option A: ASD= Shunt murmur absent, flow murmur is mid diastolic murmur. Option B: In Rheumatic- mc valve involved is Mitral & 2nd mc Aoic valve, but in 5 yr. old child only Aoic regurgitation is seen (rare) Option C: HOCM causes= Systolic murmur DCM=Functional MR & TR= Systolic Murmur Option D: Ventricular septal defect 3 varieties Muscular Membranous Supra-Cristal variety with associated with AR In 5 year child rheumtic hea disease involving isolated aoic valve is unlikely .most common valve involved in RHD is mitral valve.