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': 'Reciprocal arm serves mainly to: \nSelect and explain. \nA. To give flexibility, B. Give indirect retention, C. Counteract the forces of retentive arm, D. To give support', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]