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': 'To prevent dislodgement of abutment in distal extension RPD, it is required to have a: \nSelect and explain. \nA. Positive denture base - tissue relationship, B. Stress breaker, C. Indirect retainer, D. Multiple clasping', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]