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 ideal root-canal filling material should satisfy all of the following except which one? 
Select and explain. 
A. The material should be well tolerated by periradicular tissues, B. The material should be easily placed, C. The material should be absorbable, D. The material should be visible radiographically
C: The material should be absorbable
Answer: C: The material should be absorbable 
Explanation: Grossman's Requirements for an Ideal Root Canal Filling Material 

The material should be easily introduced into the root canal.
It should seal the canal laterally as well as apically.
It should not shrink after being inserted.
It should set slowly.
It should be impervious to moisture.
It should be bactericidal or, at least, should discourage the growth of bacteria.
It should be radiopaque.
It should not stain the tooth structure.
It should not irritate periradicular tissues or affect the tooth structure.
It should be sterile, or easily and quickly sterilized immediately before insertion.
It should be easily removable from the root canal if necessary. 

Ref: Grossman endodontics 13th ed page no 343