**Core Concept**
Statins are a group of lipid-lowering agents that primarily function by inhibiting the enzyme HMG-CoA reductase. This enzyme plays a crucial role in the biosynthesis of cholesterol in the liver. By blocking HMG-CoA reductase, statins reduce the liver's ability to produce cholesterol, thereby lowering circulating cholesterol levels.

**Why the Correct Answer is Right**
Statins exert their effects through several mechanisms:
- **Inhibition of HMG-CoA reductase**: This is the primary mechanism of action, resulting in reduced cholesterol synthesis in the liver.
- **Increased LDL receptor expression**: Statins increase the expression of LDL receptors on the surface of hepatocytes, enhancing the clearance of LDL cholesterol from the bloodstream.
- **Reduced apolipoprotein B-100 synthesis**: Apolipoprotein B-100 is a protein component of LDL cholesterol; by reducing its synthesis, statins further decrease LDL cholesterol levels.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because statins do not primarily act by increasing HDL cholesterol levels; while they may have a mild effect on HDL, this is not their primary mechanism of action.
* **Option B:** This option is incorrect because statins do not act by directly inhibiting the absorption of dietary cholesterol; they primarily affect cholesterol synthesis in the liver.
* **Option C:** This option is incorrect because statins do not primarily act by increasing triglyceride clearance; while they may have a mild effect on triglycerides, this is not their primary mechanism of action.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that statins have pleiotropic effects, including anti-inflammatory properties, improvement of endothelial function, and stabilization of atherosclerotic plaques.

**Correct Answer:** A.