Final answer:
Statins are the drugs that lower serum lipid levels by inhibiting the enzyme HMG-CoA reductase, leading to reduced cholesterol synthesis.
Step-by-step explanation:
Among the options provided, statins are the class of drugs known to lower serum lipid levels. Statins, including Atorvastatin (Lipitor) and Rosuvastatin (Crestor), function by inhibiting the enzyme HMG-CoA reductase, which is crucial for cholesterol synthesis in the body. This inhibition leads to lower levels of cholesterol produced, thus aiding in the reduction of serum lipid levels. Other drugs like nicotinic acids and bile sequestrants also have effects on lipid levels but are not listed in the provided options.