This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of lipid, Subject name: Biochemistry
Which organs do not utilise ketone bodies? 
Select and explain. 
A. Skeletal muscles, B. Cardiac muscles, C. Liver, D. RBC
D: RBC
Answer: D: RBC 
Explanation: In the fasting state, glucose must be spared for use by the central nervous system (which is largely dependent on glucose) and the red blood cells (which are wholly reliant on glucose). Therefore, tissues that can use fuels other than glucose do so; muscle and liver oxidize fatty acids and the liver synthesizes ketone bodies from fatty acids to expo to muscle and other tissues.Ref: Harper&;s Biochemistry; 30th edition; chapter 14; overview of Metabolism & the Provision of Metabolic Fuels