**Core Concept:** Abdominal distension is a clinical sign that arises due to various causes, including mechanical obstruction of the gastrointestinal (GI) tract. Intestinal obstruction is a common cause of abdominal distension, and the most important factor determining its severity and urgency of management is the type of obstruction.

**Why the Correct Answer is Right:**

The correct answer (C) refers to the most common cause of intestinal obstruction, which is **volvulus**. Volvulus is a mechanical obstruction of the GI tract caused by the rotation of an intestinal loop around its mesenteric axis. This leads to ischemia and potential necrosis of the bowel, making it a life-threatening condition. Volvulus occurs primarily in the colon (colonic volvulus) or small intestine (mesenteric volvulus). When colonic volvulus occurs, it presents with severe abdominal pain, distension, and signs of peritonitis, while mesenteric volvulus typically presents with a more subtle clinical picture.

**Why Each Wrong Option is Incorrect:**

A. **Obstructive ileus (Option A)** is not the most common cause of intestinal obstruction and is usually self-limiting. This type of obstruction occurs due to mechanical causes, such as adhesion, tumor, or hernia, but does not lead to volvulus.

B. **Intestinal obstruction due to adhesions (Option B)** is also less common than volvulus. Adhesions form after previous abdominal surgery and lead to mechanical obstruction by entrapment of the bowel. However, adhesions do not cause volvulus.

D. **Intestinal obstruction due to tumors (Option D)** can be a cause of bowel obstruction but is less common than volvulus. Tumors can obstruct the bowel by compression or invasion. However, they do not cause volvulus.

**Clinical Pearl:** Intestinal obstruction due to **volvulus** is a clinical emergency that requires prompt surgical intervention. Volvulus is a diagnostic clue in cases of acute abdomen with severe abdominal pain, distension, and signs of peritonitis. Other causes of intestinal obstruction, such as obstructive ileus, adhesions, and tumors, are typically self-limiting and do not lead to volvulus.

In the context of the question, the correct answer (C) is the most important cause of intestinal obstruction and requires prompt surgical intervention to prevent bowel necrosis and peritonitis.