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
Dry ice is 
Select and explain. 
A. Frozen CO2, B. 1,1,2,2 tetra fluoro ethylene, C. Ethyl fluoride, D. DichLoroDifluoro methane
A: Frozen CO2
Answer: A: Frozen CO2 
Explanation: None