This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
All are impoant mechanisms in the formation of lithogenic bile: 
Select and explain. 
A. Increased biliary secretion of cholesterol, B. Increased activity of HMG CoA reductase, C. Clofibrate, D. Low calorie and cholesterol rich diet
D: Low calorie and cholesterol rich diet
Answer: D: Low calorie and cholesterol rich diet 
Explanation: Mechanisms in the formation of lithogenic (stone-forming) bile. The most impoant is increased biliary secretion of cholesterol. This may occur in association with obesity, the metabolic syndrome, high-caloric and cholesterol-rich diets, or drugs (e.g., clofibrate) and may result from increased activity of hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 2617