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: Pediatrics
Which is the commonest abdominal mass in neonate : 
Select and explain. 
A. Wilm's tumor, B. Polycystic kidney, C. Neuroblastoma, D. Rhabdomyosarcoma
C: Neuroblastoma
Answer: C: Neuroblastoma 
Explanation: The commonest intra - abdominal tumor in first two years of life → Neuroblastoma.
The commonest intra - abdominal tumor between 2nd to 5th  year of life → Wilm’s tumor.
The commonest intro - abdominal tumor in children (no age specification) → Neuroblastoma.

(Wilm's tumor is the second most common abdominal tumor in children).
Remember: 
The commonest cause of abdominal mass in Newborn is Multiple dysplastic kidneys (if neoplasm or tumor has not been mentioned when asking for the commonest intra-abdominal mass, the answer will be multiple dysplastic kidneys).