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
Failure to pass meconium within 48 hrs of birth in a newborn with no obvious external abnormality should lead to the suspicion of – 
Select and explain. 
A. Anal atresia, B. Congenital pouch colon, C. Congenital aganglinosis, D. Meconium ileus
C: Congenital aganglinosis
Answer: C: Congenital aganglinosis 
Explanation: Read what Nelson says about Hirschsprung's disease (Congenital aganglionosis).
"Ninety-nine per cent of full-term infants pass meconium within 48hrs of birth. Hirschsprung disease should be suspected in any fill term infant with delayed passage of stool".