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
The impression for a diagnostic cast of a partial edentulous mouth should be taken in: 
Select and explain. 
A. Impression wax, B. Modelling compound, C. Hydro-colloid, D. Hydro cal
C: Hydro-colloid
Answer: C: Hydro-colloid 
Explanation: None