**Core Concept:**
The double bubble sign is a radiological feature that is indicative of specific gastrointestinal (GI) conditions. It occurs when two gas-filled structures, usually the stomach and the small bowel, are visualized in the rectal area on a plain abdominal radiograph or barium contrast study.

**Why the Correct Answer is Right:**
The correct answer, **C. Meckel's Diverticulum**, is the most common cause of a double bubble sign in the context of GI conditions. Meckel's Diverticulum is a remnant of the omphalomesenteric duct, present in approximately 2% of the general population. When air accumulates in Meckel's Diverticulum, it presents as a double bubble sign due to the presence of both the stomach and the small bowel in the rectal area.

**Why Each Wrong Option is Incorrect:**

A. **Diverticulitis (Diverticula)**: This is an inflammation of the diverticula, not the double bubble sign itself. Diverticula are isolated pouches in the colon wall, and their inflammation results in symptoms like abdominal pain, fever, and diarrhea, not a double bubble sign.

B. **Gastric Volvulus**: This is a rare condition where the stomach rotates around its blood supply, leading to ischemia and necrosis. Gastric volvulus usually presents with severe abdominal pain, nausea, vomiting, and sometimes shock. A double bubble sign is not a typical radiological finding in gastric volvulus.

D. **Intestinal obstruction**: While intestinal obstruction can cause a double bubble sign due to the compression of both the stomach and the small bowel, the specific condition mentioned in the correct answer, Meckel's Diverticulum, is not related to intestinal obstruction. Meckel's Diverticulum is a congenital anomaly, whereas intestinal obstruction is typically due to adhesions, tumors, or hernias.

**Clinical Pearl:** A double bubble sign on a radiograph or contrast study can be seen in a variety of GI conditions, but identifying the specific cause is crucial for appropriate management. Meckel's Diverticulum is a common cause and is usually managed conservatively, while other causes may require surgery or endoscopic intervention.

**Correct Answer: C. Meckel's Diverticulum**

Meckel's Diverticulum is a congenital anomaly present in approximately 2% of the population. When air accumulates in Meckel's Diverticulum, the double bubble sign is due to the presence of both the stomach and the small bowel in the rectal area on imaging studies. Meckel's Diverticulum is typically managed conservatively, while other causes may require surgical intervention.