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 difficulty in adopting a stainless steel crown to a\nprimary mandibular first molar is. \nSelect and explain. \nA. Wide bucco lingual contact, B. Buccal cervical ridge showing constriction, C. Prominent oblique ridge, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]