**Core Concept**
The patient's symptoms and laboratory findings suggest a diagnosis of obstructive jaundice, which is characterized by the blockage of bile flow from the liver to the duodenum. This leads to the accumulation of conjugated bilirubin in the blood, causing jaundice and elevated alkaline phosphatase levels.

**Why the Correct Answer is Right**
The blockage in the biliary tree is likely caused by a gallstone (cholelithiasis) that has migrated from the gallbladder into the common bile duct. The stone obstructs the flow of bile, leading to the buildup of conjugated bilirubin and elevated alkaline phosphatase levels. The conjugated hyperbilirubinemia is a classic feature of obstructive jaundice, which distinguishes it from pre-hepatic causes of jaundice such as hemolytic anemia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because primary biliary cirrhosis is a chronic liver disease characterized by progressive destruction of intrahepatic bile ducts, leading to cholestasis and cirrhosis. While it can cause elevated alkaline phosphatase levels, it typically presents with a more gradual onset and is not associated with gallstones.

**Option B:** This option is incorrect because pancreatic cancer can cause obstructive jaundice by compressing or invading the common bile duct. However, the patient's symptoms and laboratory findings do not provide enough evidence to support this diagnosis.

**Option C:** This option is incorrect because primary sclerosing cholangitis is a chronic liver disease characterized by inflammation and fibrosis of the intrahepatic and extrahepatic bile ducts. While it can cause obstructive jaundice, it typically presents with a more gradual onset and is not associated with gallstones.

**Clinical Pearl / High-Yield Fact**
In patients with obstructive jaundice, the presence of a palpable gallbladder (Courvoisier's sign) is highly suggestive of gallstone ileus or malignancy, rather than a benign cause such as a gallstone in the common bile duct.

**Correct Answer:** C.