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
Currently used step back technique is modified, it was given by: 
Select and explain. 
A. Clam, B. Wein, C. Schilder, D. Mullaney
D: Mullaney
Answer: D: Mullaney 
Explanation: None