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
[{'content': 'Plaque differs from materia alba in \nSelect and explain. \nA. Presence of bacteria, B. Presence of glycoprotein, C. Presence of saliva, D. Absence of glycoprotein', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]