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
Type III Dental gypsum is 
Select and explain. 
A. Class II stone, B. Densite, C. Class I stone or hydrocal, D. Model or lab plaster
C: Class I stone or hydrocal
Answer: C: Class I stone or hydrocal 
Explanation: Type 3 OR dental stone, model
Synonym  Class I stone or Hydrocal 
Uses
For preparing master casts and to make molds.