This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of carbohydrate, Subject name: Biochemistry
Which mucopolysaccharides does not contain uronic acid? 
Select and explain. 
A. Hyaluronic acid, B. Chondroitin sulfate, C. Dermatan sulfate, D. Keratan sulfate
D: Keratan sulfate
Answer: D: Keratan sulfate 
Explanation: None