**Core Concept**
Hirschsprung's disease is a congenital condition characterized by the absence of ganglion cells in the distal colon, leading to a functional obstruction. The absence of these cells results in a failure of the normal peristaltic movement and relaxation of the distal sigmoid colon, causing a classic clinical presentation.

**Why the Correct Answer is Right**
The most common presentation of Hirschsprung's disease in infants is a failure to pass meconium within the first 48 hours of life, followed by abdominal distension, vomiting, and constipation. This is due to the accumulation of stool in the colon proximal to the aganglionic segment, which cannot pass through. The absence of ganglion cells disrupts the normal enteric nervous system, leading to a failure of peristalsis and relaxation of the distal colon.

**Why Each Wrong Option is Incorrect**
**Option A:** Failure to pass meconium within the first 24 hours of life is a common presentation, but not the most specific or sensitive indicator.
**Option B:** Diarrhea is not typically associated with Hirschsprung's disease, as the obstruction prevents stool from passing through.
**Option C:** Abdominal pain is not a primary symptom of Hirschsprung's disease, although it may occur in some cases.

**Clinical Pearl / High-Yield Fact**
Remember, the "rule of 48" for Hirschsprung's disease: failure to pass meconium within 48 hours of life should raise suspicion for this condition.

**Correct Answer: C. Abdominal distension, vomiting, and constipation.**