Dry ice is-

1. Solid NH3

2. Solid SO2

3. Solid CO2

4. Solid N2



Hint: Carbon dioxide in solid state 

Carbon dioxide can be obtained as a solid in the form of dry ice allowing the liquified CO2 to expand rapidly.

 Dry ice is often used as it offers extended cooling for the payload and can be 4 times less than the average cost of transport by mechanical refrigerated means.