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': 'Changes in the gingiva during pregnancy are attributed to \nSelect and explain. \nA. Changes in the hormonal level, B. Altered microorganisms, C. Altered immunological responses level, D. All the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]