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
Instrument used for gingival retraction during rubber
dam placement is 
Select and explain. 
A. retainer no:208, B. retainer no:210, C. retainer no:212, D. retainer no:216
C: retainer no:212
Answer: C: retainer no:212 
Explanation: None