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': 'Which of the following metal is considered as the principal hardener and gives red colour to the alloy? \nSelect and explain. \nA. Platinum, B. Palladium, C. Copper, D. Zinc', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Copper when added to gold-based alloys, imparts a reddish color to the gold and hardens the alloy via a solid-solution or ordered-solution mechanism.\nRef: Craig’s 14th edition page 183, 184', 'role': 'assistant'}]