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': 'In periodontal ligament there is: \nSelect and explain. \nA. Type I collagen, B. Type II collagen, C. Type III collagen, D. Type IV collagen', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]