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
All are advantages of removable space maintainers EXCEPT 
Select and explain. 
A. Easy to clean, B. Permit maintenance of proper oral hygiene, C. They maintain vertical dimension, D. Band construction is necessary
D: Band construction is necessary
Answer: D: Band construction is necessary 
Explanation: None