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
In plaster of paris, the setting time is primarily altered by: 
Select and explain. 
A. Altering P/L ratio, B. Altering temperature of mixing water, C. Speed and length of hand spatulation, D. Addition of accelerators and retarders
D: Addition of accelerators and retarders
Answer: D: Addition of accelerators and retarders 
Explanation: Chemical modifiers have been used extensively to increase or decrease the setting time of gypsum products; they are called retarders and accelerators respectively. The manufacturers use both types of compounds to formulate gypsum products with specific setting times.
Reference: PHILLIPS’ SCIENCE OF DENTAL MATERIALS, 12th ed page no 186