Brain fuel in prolonged starvation

After about three weeks of starvation, the brain gets a large share of its energy from ketone bodies. What is the main benefit?

1. AIt allows the brain to oxidize fatty acids directly✕
2. BIt increases glycogen stores in the liver✕
3. CIt reduces the need to break down muscle protein for gluconeogenesis✕
4. DIt raises blood glucose above normal✕