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 one of the following acids is generally recommended for etching tooth structure? \nSelect and explain. \nA. Maleic acid, B. Polyacrylic acid, C. Phosphoric acid, D. Tartaric acid', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Although some of the self-etch bonding systems use milder acid, the primary acid system used for etching tooth structure is phosphoric acid.', 'role': 'assistant'}]