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: Dental
Caries detection dye can stain the following except: 
Select and explain. 
A. Granular necrotic tissue, B. Dry, leathery dentin, C. Reversibly denatured collagen, D. Irreversibly denatured collagen
C: Reversibly denatured collagen
Answer: C: Reversibly denatured collagen 
Explanation: None