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
Cobra head sign on IVP is classically seen with 
Select and explain. 
A. Ureterocele, B. Ectopic ureter, C. Horse shoe kidney, D. Medullary sponge kidney
A: Ureterocele
Answer: A: Ureterocele 
Explanation: Cobra head sign / Adder head / Snake appearance.