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': 'Class IV cavity: \nSelect and explain. \nA. Occurs on the proximal surface not involving the incisal edge of anterior teeth, B. Occurs on proximal surface involving the incisal edge of anterior teeth, C. Occurs on proximal surface involving the incisal edge of posterior teeth, D. Involves the buccal surface of Anterior and posterior teeth', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]