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
Sulcus bleeding index measures: 
Select and explain. 
A. Gingivitis, B. Dental plaque, C. Gingival bleeding, D. Gingival recession
C: Gingival bleeding
Answer: C: Gingival bleeding 
Explanation: None