**Core Concept**
The double bubble sign is a radiological finding on abdominal X-ray or contrast study characterized by two distinct air-filled bubbles in the gastrointestinal tract — one in the distal stomach and one in the proximal duodenum. It indicates obstruction proximal to the duodenum and is associated with congenital anomalies of the gastrointestinal tract.

**Why the Correct Answer is Right**
The double bubble sign is classically seen in duodenal atresia due to complete obstruction of the duodenum. It can also be seen in annular pancreas, where the pancreatic ring compresses the duodenum, causing obstruction. Ladd’s band, a congenital band of peritoneal tissue, can cause obstruction of the distal duodenum and present with the same radiological appearance. Thus, all listed conditions may manifest with this sign.

**Why Each Wrong Option is Incorrect**
Option A: Ladd’s band may cause obstruction and present with a double bubble sign, so it is not incorrect.
Option B: Annular pancreas causes duodenal compression and can produce the double bubble sign, so it is not incorrect.
Option C: Duodenal atresia is the most classic cause and is strongly associated with the sign, so it is not incorrect.
Since all three conditions can present with the double bubble sign, "All of the above" is the most accurate and comprehensive choice.

**Clinical Pearl / High-Yield Fact**
The double bubble sign is a hallmark of duodenal atresia and should prompt immediate surgical evaluation. It is often seen in neonates with abdominal distension and vomiting, and its presence necessitates urgent intervention. It is not specific to one condition but is a key radiological clue in congenital GI obstruction.

✓ Correct Answer: D. All of the above