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
Which of the following impression material is rigid? 
Select and explain. 
A. Zinc oxide-eugenol, B. Reversible hydrocolloid, C. Alginate, D. Polysulphide rubber
A: Zinc oxide-eugenol
Answer: A: Zinc oxide-eugenol 
Explanation: Key Concept: ZnO Eugenol impression paste is rigid (inelastic) impression material.