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: Biochemistry
In prolonged starvation the main energy source of brain is: 
Select and explain. 
A. Glucose, B. Ketone bodies, C. Fructose, D. Fatty acids
B: Ketone bodies
Answer: B: Ketone bodies 
Explanation: STARVE FEED CYCLE
Divided into 5 stages:

Well-fed state (1–4 hours after food)
Early fasting (4–16 hours after food)
Fasting (16–48 hours after food)
Starvation (2–3 days without food)
Prolonged starvation (> 5 days without food).