**Core Concept**
Budd-Chiari syndrome is a rare condition characterized by the occlusion of the hepatic veins, which are responsible for draining blood from the liver into the inferior vena cava. This occlusion leads to increased pressure within the liver, causing various symptoms such as abdominal pain, ascites, and liver enlargement.

**Why the Correct Answer is Right**
The occlusion in Budd-Chiari syndrome typically occurs at the level of the hepatic veins, which are the smallest and most distal part of the venous system draining the liver. The hepatic veins are formed by the confluence of the right, middle, and left hepatic veins, which arise from the liver sinusoids. The occlusion can be caused by a variety of factors, including thrombosis, webs, or tumors. The correct answer is related to the anatomical location where the occlusion occurs.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the occlusion in Budd-Chiari syndrome is not typically located at the level of the portal vein, which is a different part of the hepatic circulation.
**Option B:** This option is incorrect because the occlusion is not usually located at the level of the hepatic artery, which supplies oxygen and nutrients to the liver.
**Option C:** This option is incorrect because the occlusion is not typically located at the level of the inferior vena cava, which is the vessel into which the hepatic veins drain.

**Clinical Pearl / High-Yield Fact**
Budd-Chiari syndrome can be caused by a variety of factors, including thrombophilia, cancer, and trauma. It is essential to identify the underlying cause of the occlusion to provide appropriate treatment and prevent complications.

**Correct Answer:** C. The hepatic veins are the correct location of the occlusion in Budd-Chiari syndrome.