under prolonged starvation brain receive energy from 

Q.Under prolonged starvation, brain receive energy from
(a) Carbohydrates 
(b) Fats 
(c) Proteins 
(d) Acetoacetate .

Under prolonged starvation the brain uses ketone bodies (acetoacetate, beta-hydroxybutyrate and acetone) as source of energy. These are produced by liver from fatty acids.

So, the correct answer is  (d) Acetoacetate