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': 'Most common reason to repeat impression is? \nSelect and explain. \nA. Improper positioning of tray, B. Too Less or excess material, C. Voids that are irreparable, D. Improper mixing', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]