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 carat of gold foil used for restoration: \nSelect and explain. \nA. 24, B. 18, C. 20, D. 16', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The direct filling gold is 99.99% pure which is similar to 24 carat gold. Carat refers to the parts of pure gold in 24 parts of an alloy. 24-karat gold is pure gold, whereas 22-karat gold is an alloy containing 22 parts pure gold and 2 parts of other metals.', 'role': 'assistant'}]