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 zinc polycarboxylate modified setting time and \nincreased manipulative properties are due to \nSelect and explain. \nA. Bismuth Oxide, B. Stannic Oxide, C. Magnesium Oxide, D. Stannous Oxide', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]