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
Lactobacilli are numerous in carious lesions because they 
Select and explain. 
A. Are the main causative agent, B. Can produce insoluble extracellular polysaccharides, C. Can attach to smooth enamel surfaces, D. Are secondary invaders
D: Are secondary invaders
Answer: D: Are secondary invaders 
Explanation: None