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
Majority of oral microorganisms are: 
Select and explain. 
A. Strict anaerobes, B. Gram-positive bacilli, C. Spirochetes, D. Facultative anaerobes
D: Facultative anaerobes
Answer: D: Facultative anaerobes 
Explanation: None