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.