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
Sending the parents outside the operatory and threatening the child that they won't be back until he stops crying-is an example of which of the following behavior management techniques: 
Select and explain. 
A. Omission, B. Negative reinforcement, C. Positive reinforcement, D. Modelling
A: Omission
Answer: A: Omission 
Explanation: None