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
By product formed when gypsum binding investment material is heated above 1200 degree centigrade: 
Select and explain. 
A. SO3, B. CO, C. SO2, D. All of the above.
A: SO3
Answer: A: SO3 
Explanation: If heated above 700 degree centigrade then CO & SO2 are formed.