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': 'Indirect retainers in bilateral distal extension base removable partial dentures are based on: \nSelect and explain. \nA. Class I lever principle, B. Class II lever principle, C. Class III lever principle, D. Combination of more than one of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]