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': 'Factors which contribute to the risk of developing periodontal disease in individual teeth include \nSelect and explain. \nA. Occlusion, B. Excessive occlusal stress, C. Pulpal infections, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]