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
[{'content': 'Which of the following is also known as first dental elastomers? \nSelect and explain. \nA. Polysulphides, B. Condensation silicone, C. Addition silicone, D. Polyether', 'role': 'user'}, {'content': 'Answer: A \nExplanation: POLYSULFIDES:\nThis was the first elastomeric impression material to be introduced (1950). It is also known as Mercaptan or Thiokol.', 'role': 'assistant'}]