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 most frequent complaint of patients shortly after amalgam restorations are placed is: \nSelect and explain. \nA. Pain on percussion, B. An open contact point, C. Cold sensitivity, D. Numbness around the gingiva', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]