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
The terminal end of a retentive arm is optimally placed
at 
Select and explain. 
A. Middle of the gingival third of the clinical crown, B. Middle of the middle third of the clinical crown, C. Under the gingival sulcus in the clean area, D. Middle of occlusal third of the clinical crown
A: Middle of the gingival third of the clinical crown
Answer: A: Middle of the gingival third of the clinical crown 
Explanation: None