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
Which of the following is not a marking in Michigam O probe 
Select and explain. 
A. 3, B. 6, C. 8, D. 9
D: 9
Answer: D: 9 
Explanation: Mischigam O probe is a manual probe having marking 3,6,8.