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: Anatomy
Which of the following does not form the ground substance 
Select and explain. 
A. Glycosaminoglycans, B. Collagen fibers, C. Proteoglycans, D. Multiadhesive glycoproteins
B: Collagen fibers
Answer: B: Collagen fibers 
Explanation: None