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': 'Dimension stability of hydrocollids may be achieved by \nSelect and explain. \nA. optimizing w:p, B. using cold water, C. prolonged manipulation, D. using humidor', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]