**Core Concept**
Intestinal obstruction in children can be caused by various factors, including congenital anomalies, foreign bodies, and acquired conditions. The most common cause is often related to the anatomical narrowing of the intestinal lumen, which can lead to complete or partial blockage of the normal flow of intestinal contents.

**Why the Correct Answer is Right**
The correct answer is intussusception, a condition where a part of the intestine invaginates into another section, causing a mechanical obstruction. Intussusception occurs when the ileocecal valve is involved, leading to a telescoping effect of the ileum into the cecum. This can cause severe abdominal pain, vomiting, and bloody stools in children. The exact cause of intussusception is often idiopathic, but it may be related to viral infections or other underlying conditions.

**Why Each Wrong Option is Incorrect**
* **Option A:** Volvulus is a twisting of the intestine that can cause obstruction, but it is less common in children compared to intussusception.
* **Option B:** Gastrointestinal foreign bodies can cause obstruction, but they are more common in older children and adults.
* **Option C:** Meckel's diverticulum is a congenital anomaly that can cause intestinal bleeding, but it is not the most common cause of acute intestinal obstruction in children.

**Clinical Pearl / High-Yield Fact**
The "3 Ps" of intussusception are: pain, palpable mass, and peristaltic waves, which are often seen in children with this condition.

**Correct Answer: C. Intussusception**