**Core Concept**
Courvoisier's law states that a palpably distended gallbladder in the presence of obstructive jaundice is indicative of malignant obstruction of the bile ducts. This law is based on the principle that malignant obstruction of the bile ducts is typically associated with a non-inflamed and distended gallbladder due to the lack of inflammation and fibrosis.

**Why the Correct Answer is Right**
The correct answer is an exception to Courvoisier's law because it represents a situation where a distended gallbladder is not associated with malignant obstruction of the bile ducts. This is typically seen in cases of obstructive jaundice due to gallstones, where the gallbladder becomes distended due to the obstruction of bile flow. In these cases, the gallbladder may be inflamed and tender, unlike the non-inflamed and distended gallbladder seen in malignant obstruction.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a classic example of Courvoisier's law, where a distended gallbladder is associated with malignant obstruction of the bile ducts.
**Option B:** This option is incorrect because it is a condition that is not typically associated with a distended gallbladder, and therefore does not represent an exception to Courvoisier's law.
**Option C:** This option is incorrect because it is a condition that is typically associated with a non-distended gallbladder, and therefore does not represent an exception to Courvoisier's law.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that Courvoisier's law is not absolute and can be exceptions, such as obstructive jaundice due to gallstones, where the gallbladder may be inflamed and tender. A high index of suspicion is necessary to diagnose the underlying cause of obstructive jaundice.

**Correct Answer: B. Pancreatic cancer is an exception to Courvoisier's law, as a distended gallbladder can be associated with pancreatic cancer causing obstructive jaundice.**