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
During conversion of glycerol to pyruvic acid, the first glycolytic intermediate to form is: 
Select and explain. 
A. 2 - phospho glyceric acid, B. 3 - phospho glyceric acid, C. 3 - phospho glyceraldehyde, D. Dihydroxy acetone phosphate
D: Dihydroxy acetone phosphate
Answer: D: Dihydroxy acetone phosphate 
Explanation: None