**Core Concept**
The IVC (Inferior Vena Cava) is a major vein that receives deoxygenated blood from the lower and middle body, returning it to the heart. The IVC is formed by the confluence of the right common iliac veins and has several tributaries that drain into it.

**Why the Correct Answer is Right**
The correct answer is the hepatic vein. The hepatic veins are responsible for draining the deoxygenated blood from the liver into the IVC. This process is crucial for maintaining liver function and overall cardiovascular health. The hepatic veins are formed by the confluence of smaller hepatic veins that drain the liver sinusoids, and they play a vital role in the liver's detoxification and metabolic processes.

**Why Each Wrong Option is Incorrect**
* **Option A:** The renal veins drain into the IVC, but they are not the primary vein draining into it. The renal veins are responsible for draining the deoxygenated blood from the kidneys into the IVC.
* **Option B:** The superior mesenteric vein primarily drains into the portal vein, not the IVC. The portal vein carries blood from the gastrointestinal tract to the liver for detoxification and metabolic processes.
* **Option D:** The axillary veins drain into the subclavian veins, which then drain into the brachiocephalic veins. The brachiocephalic veins ultimately drain into the superior vena cava, not the IVC.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the hepatic veins are responsible for draining the liver, and their obstruction can lead to liver congestion and dysfunction. This is a critical concept for students of internal medicine and surgery.

**Correct Answer: C. Hepatic vein. Hepatic veins drain into the IVC.**