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
Band and loop space maintainer is: 
Select and explain. 
A. Unilateral fixed non functional, B. Unilateral removable functional, C. Bilateral fixed non functional, D. Bilateral removable functional
A: Unilateral fixed non functional
Answer: A: Unilateral fixed non functional 
Explanation: None