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
Mechanism of action of pit and fissures sealant is by: 
Select and explain. 
A. Blocking the nutrient supply to bacteria, B. Killing micro-organism causing caries, C. Neutralising acid produced by bacteria, D. All of these
A: Blocking the nutrient supply to bacteria
Answer: A: Blocking the nutrient supply to bacteria 
Explanation: None