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': 'The soldering temperature for orthodontic silver solders is between: \nSelect and explain. \nA. 550-555 degree Celsius, B. 720-775 degree Celsius, C. 670-675 degree Celsius, D. 595-600 degree Celsius', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Silver-based solders are used when a low-fusing point is needed for soldering onto stainless steel or\xa0other base metal alloys. Orthodontic appliances are commonly soldered using silver-based solders. In\xa0general, the resistance of silver solders to tarnish is not as good as gold-based solders. The silver-based solders are composed of silver (10 to 80 wt%), copper (15 to 30%) and zinc (4 to 35%), with\xa0 some products containing small percentages of cadmium, tin or phosphorus to further modify the\xa0fusion temperature. The formation of the silver-copper eutectic is responsible for these solders to range\xa0from 620° to 700°C, which is slightly below those of gold-based solders. This diﬀerence is important in\xa0 the soldering of stainless steel.', 'role': 'assistant'}]