**Core Concept**
Lovastatin is a statin, a class of lipid-lowering medications that inhibit the synthesis of cholesterol in the liver. This reduction in cholesterol production is achieved by targeting a key enzyme involved in the mevalonate pathway, which is responsible for cholesterol biosynthesis.

**Why the Correct Answer is Right**
Lovastatin specifically inhibits HMG-CoA reductase, an enzyme that catalyzes the conversion of HMG-CoA to mevalonate. This step is a crucial regulatory point in the cholesterol biosynthesis pathway. By inhibiting HMG-CoA reductase, lovastatin reduces the production of cholesterol in the liver, resulting in decreased levels of low-density lipoprotein (LDL) cholesterol in the bloodstream. This mechanism of action is unique to statins and is responsible for their lipid-lowering effects.

**Why Each Wrong Option is Incorrect**
**Option A:** HMG-CoA synthetase is another enzyme involved in the mevalonate pathway, but it is not the target of statins like lovastatin. Inhibiting this enzyme would have different effects on cholesterol biosynthesis.

**Option C:** While muscle pain (myalgia) and myopathy are potential side effects of statin therapy, myositis (inflammation of muscle tissue) is a less common but serious adverse effect. Lovastatin may cause myopathy, but this is not a direct result of its use.

**Option D:** Lovastatin does decrease the synthesis of cholesterol, but it does not cause lenticular opacity (cataract formation). This is a potential side effect of other medications, such as corticosteroids or certain antibiotics.

**Clinical Pearl / High-Yield Fact**
When prescribing statins, it's essential to be aware of potential side effects, including myopathy and liver enzyme elevations. Regular monitoring of liver function tests and muscle enzymes can help identify these issues early, allowing for timely adjustments to treatment.

**✓ Correct Answer:** B. Inhibits HMG CoA reductase