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': 'Dimensional stability of hydrocolloid impressions may be achieved by: \nSelect and explain. \nA. Using less water powder ratio, B. Storing the impression under water, C. Prolonged manipulation, D. Using humidor', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]