**Core Concept**
Raising high-density lipoprotein (HDL) cholesterol levels is a therapeutic goal in managing dyslipidemia, as it is associated with reduced cardiovascular risk. HDL cholesterol plays a crucial role in reverse cholesterol transport, where it helps in removing excess cholesterol from peripheral tissues and transporting it to the liver for excretion.

**Why the Correct Answer is Right**
Niacin (nicotinic acid) is a well-established agent for increasing HDL cholesterol levels. It acts by inhibiting the breakdown of HDL in the bloodstream and promoting its synthesis. Niacin also has a moderate effect on reducing triglyceride levels and increasing LDL particle size, making it a useful agent in managing mixed dyslipidemia. Additionally, niacin has anti-inflammatory properties, which may contribute to its cardiovascular benefits.

**Why Each Wrong Option is Incorrect**
**Option A:** Statins, such as atorvastatin, primarily lower LDL cholesterol levels but have a minimal effect on HDL cholesterol. They may even decrease HDL levels in some cases.
**Option B:** Fibrates, like fenofibrate, are effective in lowering triglyceride levels but have a limited effect on HDL cholesterol. They may even decrease HDL levels in some cases.
**Option C:** Bile acid sequestrants, such as cholestyramine, primarily lower LDL cholesterol levels by binding to bile acids in the intestine but have a minimal effect on HDL cholesterol.

**Clinical Pearl / High-Yield Fact**
Niacin's ability to raise HDL cholesterol levels is a key factor in its cardiovascular benefits. However, its use is limited by side effects, including flushing, gastrointestinal symptoms, and glucose intolerance. A lower dose of extended-release niacin (1.5-2 g daily) may be used to minimize side effects while maintaining efficacy.

**Correct Answer:** C. Niacin.