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 used for removing sub gingival calculus 
Select and explain. 
A. Sickle scalers, B. Hoe, C. Chisel, D. File scaler
A: Sickle scalers
Answer: A: Sickle scalers 
Explanation: None