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': 'Before inserting the loaded tray with impression compound the temperature is usually checked: \nSelect and explain. \nA. Against the back of operator’s hand, B. Against the hand of patient, C. By placing directly in mouth, D. By immersion in boiling water', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]