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 “Shoe Leather Survey” was given by 
Select and explain. 
A. Trendley H. Dean, B. Frederick McKay, C. Greene Black, D. J. M. Eager
A: Trendley H. Dean
Answer: A: Trendley H. Dean 
Explanation: Fluoride was established as the causative factor for mottling of enamel through the historical studies conducted by Trendley H. Dean, known  as the "Shoe Leather Survey".