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': 'Terminal end of retentive arm of extra coronal retainer is\nplaced at \nSelect and explain. \nA. Gingival third, B. Occlusal third, C. Middle third, D. Junction of middle & Gingival third', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]