**Core Concept:**
Intestinal obstruction is a clinical condition where the passage of contents through the small intestine or large intestine is obstructed, leading to abdominal distension, pain, and potentially complications like volvulus, necrosis, or perforation. The primary cause of intestinal obstruction can be categorized into mechanical and obstructions due to functional or organic causes.

**Why the Correct Answer is Right:**
The correct answer is B (intussusception) because intussusception is a specific type of mechanical obstruction caused by the telescoping of a portion of the intestine into the adjacent part, typically due to a lead point (a mass, lesion, or retained foreign body). This leads to the obstruction of intestinal contents, causing abdominal distension and pain.

**Why Each Wrong Option is Incorrect:**
A. Obstruction due to adhesions (not the primary cause, usually secondary to previous surgery or inflammation)
C. Obstruction due to hernias (not the primary cause, usually caused by external compression)
D. Obstruction due to tumors (not the primary cause, usually secondary to compression or invasion)

**Clinical Pearl:**
Intussusception is a rare cause of intestinal obstruction, often diagnosed through clinical suspicion and confirmed with imaging studies like X-ray, USG, or CT scan. Early recognition and management are crucial to prevent complications like bowel necrosis and perforation.

**Correct Answer:** B (intussusception)