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
An example of unilateral fixed space maintainer is: 
Select and explain. 
A. Crown and loop space maintainer, B. Nance palatal arch, C. Lingual arch space maintainer, D. Transpalatal arch
A: Crown and loop space maintainer
Answer: A: Crown and loop space maintainer 
Explanation: All other options are bilateral space maintainers.