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 is also known as first dental elastomers? 
Select and explain. 
A. Polysulphides, B. Condensation silicone, C. Addition silicone, D. Polyether
A: Polysulphides
Answer: A: Polysulphides 
Explanation: POLYSULFIDES:
This was the first elastomeric impression material to be introduced (1950). It is also known as Mercaptan or Thiokol.