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
Bacteria invading after S. mutans: 
Select and explain. 
A. Streptococcus sanguis., B. Lactobacillus., C. Actinomyces., D. All of the above.
A: Streptococcus sanguis.
Answer: A: Streptococcus sanguis. 
Explanation: None