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 direct retainer of choice when the principle abutment tooth has Lost its periodontal support is: \nSelect and explain. \nA. Embrasure clasp, B. Ring clasp, C. Multiple circlet clasp, D. Onlay clasp', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]