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': 'A gingival wall is difficult to obtain in primary molar\nwhen it extends too far gingivally in class II cavities\nbecause \nSelect and explain. \nA. Facial pulp horn may be exposed, B. b)\tInclination of cervical enamel rods occlusally, C. Of marked cervical constriction, D. Prime contact is broad and flat', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]