**Core Concept**
A Whipple's operation, also known as a pancreaticoduodenectomy, is a complex surgical procedure that involves the removal of a portion of the pancreas, the duodenum, the head of the pancreas, and other surrounding tissues. This operation is typically performed to treat pancreatic cancer, ampullary cancer, and other conditions affecting the pancreas and bile ducts.

**Why the Correct Answer is Right**
The portal vein is not resected in a Whipple's operation. The portal vein is a vital blood vessel that carries blood from the gastrointestinal tract to the liver. The surgeon must carefully preserve the portal vein to maintain blood flow to the liver. In a Whipple's operation, the surgeon typically resects the duodenum, the head of the pancreas, and the common bile duct, but the portal vein is spared. This is because the portal vein is a key structure that supplies blood to the liver, and its resection would be catastrophic.

**Why Each Wrong Option is Incorrect**
**Option A:** The duodenum is indeed resected in a Whipple's operation. The duodenum is the first portion of the small intestine and is closely associated with the pancreas and bile ducts. It is removed as part of the surgical procedure to ensure that all cancerous tissue is eliminated.

**Option B:** The head of the pancreas is also resected in a Whipple's operation. The head of the pancreas is the portion of the pancreas that is located near the duodenum and bile ducts. It is typically removed in its entirety to ensure that all cancerous tissue is eliminated.

**Option D:** The common bile duct is resected in a Whipple's operation. The common bile duct is a vital structure that carries bile from the liver to the small intestine. It is closely associated with the pancreas and is typically removed as part of the surgical procedure.

**Clinical Pearl / High-Yield Fact**
A key aspect of a Whipple's operation is the preservation of the portal vein. Surgeons must carefully dissect the portal vein to ensure that it is not damaged or resected. This requires great skill and precision, as the consequences of portal vein injury can be catastrophic.

**✓ Correct Answer:** C. Portal vein