**Core Concept**
The triangle of Calot is a critical anatomical landmark in the surgical field during cholecystectomy, defined by its boundaries: the common hepatic duct medially, the cystic duct inferiorly, and the liver superiorly. This triangle is essential for the safe identification and ligation of the cystic duct and artery.

**Why the Correct Answer is Right**
The structure that courses through the triangle of Calot is the cystic artery. The cystic artery typically arises from the right hepatic artery, which in turn branches from the hepatic artery proper. It then passes through the triangle of Calot to reach the gallbladder, where it supplies blood to the cystic duct and the gallbladder wall. The cystic artery's location within the triangle of Calot is crucial for the surgeon to identify and ligate it to prevent bleeding during the operation.

**Why Each Wrong Option is Incorrect**
**Option A:** The common bile duct does not course through the triangle of Calot. Instead, it is located posteriorly to the cystic duct and common hepatic duct, forming the common bile duct.

**Option B:** The right hepatic artery does give rise to the cystic artery, but it is not the structure that courses through the triangle of Calot. The right hepatic artery itself is located anterior to the hepatic artery proper.

**Option D:** The portal vein does not course through the triangle of Calot. It is a major vein that carries blood from the gastrointestinal tract to the liver, but it is not a structure that passes through the triangle of Calot.

**Clinical Pearl / High-Yield Fact**
The triangle of Calot is a critical landmark in cholecystectomy, and the surgeon must carefully identify and ligate the cystic artery to prevent bleeding. A mnemonic to remember the boundaries of the triangle of Calot is "Common Hepatic Duct Medially, Cystic Duct Inferiorly, Liver Superiorly".

**Correct Answer: C. Cystic artery.