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
Activity index of GCF shows ? 
Select and explain. 
A. IL-B/IL-RC, B. IL-RC/IL-B, C. RANK / OPG, D. OPG/ RANK
A: IL-B/IL-RC
Answer: A: IL-B/IL-RC 
Explanation: None