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
What are the characteristics of the primary (initial) bacterial colonizers of the tooth in dental plaque formation? 
Select and explain. 
A. Gram-negative facultative, B. Gram-positive facultative, C. Gram-negative anaerobic, D. Gram-positive anaerobic
B: Gram-positive facultative
Answer: B: Gram-positive facultative 
Explanation: Streptococcal and Actinomyces species are initial colonizers of dental plaque. They are grampositive, facultative micro-organisms.