**Core Concept**
Obstructive jaundice in children is a condition characterized by the blockage of bile flow, leading to a buildup of bilirubin in the blood and tissues. The most common cause of this condition in children is a congenital anomaly or acquired obstruction of the bile ducts.

**Why the Correct Answer is Right**
The most common cause of obstructive jaundice in children is a biliary atresia, a condition where there is a complete or partial absence of the bile ducts. This can be congenital or acquired, often resulting from a viral infection or an inflammatory process. The obstruction can occur at the level of the bile ducts within the liver (intrahepatic) or outside the liver (extrahepatic). In children, biliary atresia is the leading cause of obstructive jaundice, often presenting with jaundice, dark urine, and pale stools.

**Why Each Wrong Option is Incorrect**
* **Option A:** Choledochal cysts are a rare congenital anomaly of the bile ducts, leading to dilatation and potential obstruction. However, they are not the most common cause of obstructive jaundice in children.
* **Option B:** Neonatal hepatitis is an inflammation of the liver in newborns, often caused by viral infections. While it can lead to jaundice, it is not typically associated with obstructive jaundice.
* **Option C:** Gallstones are a common cause of obstructive jaundice in adults but are rare in children.

**Clinical Pearl / High-Yield Fact**
Biliary atresia is a medical emergency requiring prompt diagnosis and intervention to prevent liver cirrhosis and failure. Early signs of biliary atresia include jaundice, dark urine, and pale stools, often presenting within the first few weeks of life.

**Correct Answer: C. Gallstones are a common cause of obstructive jaundice in adults but are rare in children.