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: Pathology
Animals maintained in a germ free environment did not develop caries even when fed on a high carbohydrate diet is given by: 
Select and explain. 
A. Gottlieb., B. Miller., C. Synder., D. Orland and Fizgerald.
D: Orland and Fizgerald.
Answer: D: Orland and Fizgerald. 
Explanation: None