**Core Concept**
The definitive diagnosis of extrahepatic biliary atresia (EHBA) requires a histopathological examination of the liver tissue to confirm the presence of bile duct atresia and portal fibrosis. EHBA is a congenital anomaly characterized by the obstruction of the bile ducts outside the liver, leading to bile duct destruction and liver damage.

**Why the Correct Answer is Right**
Liver biopsy is the gold standard for diagnosing EHBA because it allows for the direct examination of liver tissue, which is essential for confirming the diagnosis. Histopathological examination of the liver tissue can reveal the characteristic features of EHBA, including bile duct atresia, portal fibrosis, and bile duct proliferation. The liver tissue obtained from the biopsy can also be stained with special stains, such as orcein or Masson's trichrome, to highlight the bile ducts and confirm their absence or destruction.

**Why Each Wrong Option is Incorrect**
**Option A:** Peroperative cholangiography is a diagnostic technique that involves injecting a contrast agent into the bile ducts during surgery to visualize the bile ducts on an X-ray. While it can provide information about the anatomy of the bile ducts, it is not a definitive diagnostic test for EHBA.

**Option B:** Hepatobiliary scintigraphy is a nuclear medicine test that uses a radioactive tracer to visualize the liver and bile ducts. While it can provide information about the function of the liver and bile ducts, it is not a definitive diagnostic test for EHBA.

**Option C:** Alkaline phosphatase level is a blood test that measures the level of an enzyme called alkaline phosphatase in the blood. Elevated levels of alkaline phosphatase can indicate bile duct obstruction or damage, but it is not a definitive diagnostic test for EHBA.

**Clinical Pearl / High-Yield Fact**
Liver biopsy is a crucial diagnostic tool in pediatric hepatology, and it plays a key role in the diagnosis and management of various liver diseases, including EHBA. The biopsy sample obtained should be examined by a pathologist experienced in pediatric liver pathology to ensure accurate diagnosis.

**Correct Answer:**
✓ Correct Answer: D. Liver biopsy