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: Physiology
CSF sugar is - 
Select and explain. 
A. Half of blood sugar, B. 1/3 of blood sugar, C. 2/3 of blood sugar, D. Same as blood sugar
C: 2/3 of blood sugar
Answer: C: 2/3 of blood sugar 
Explanation: Ans is'c' i.e.,2/3 of blood sugarCSF / plasma glucose ratio is 0.64.