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
Factor responsible for pregnancy gingivitis is: 
Select and explain. 
A. Hormonal imbalance, B. Micro-organism associated with plaque, C. Poor oral hygiene, D. Drugs
B: Micro-organism associated with plaque
Answer: B: Micro-organism associated with plaque 
Explanation: None