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 rubber dam is particularly adaptable to the primary\nsecond molar because the: \nSelect and explain. \nA. Occluso cervical height favours its retention, B. Cervical constriction of the crown favours its retention, C. Mesiobuccal bulge favours its retention, D. Smaller diameter of the crown (as compared to permanent teeth) favours its retention', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]