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
The closest speaking space was suggested by: 
Select and explain. 
A. Pound, B. McGrane, C. Neswonger, D. Silverman
D: Silverman
Answer: D: Silverman 
Explanation: The space between the teeth during casual repetition of the sound “s”. It is considered the closest relationship of the occlusal surfaces and incisal edges of the mandibular teeth to the maxillary teeth during function and rapid speech.
This phonetic method is one of the several techniques to determine vertical dimension of occlusion in dentate and edentate patients. This method was proposed by Silverman.