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
Energy yield of fats is 
Select and explain. 
A. 4 kcal per gram, B. 6 kcal per gram, C. 8 kcal per gram, D. 9 kcal per gram
D: 9 kcal per gram
Answer: D: 9 kcal per gram 
Explanation: Carbohydrates and proteins - 4 kcal per gram.
Fats - 9 kcal per gram.