What is dry ice primarily composed of?

Dry ice is primarily composed of solid carbon dioxide. It is created by compressing and cooling carbon dioxide gas, which then transitions directly into a solid state at temperatures below -78.5 degrees Celsius. Unlike regular ice, which is made from frozen water, dry ice sublimates, meaning it transitions from a solid to a gas without passing through a liquid phase. This property makes dry ice useful for refrigeration and shipping perishable goods, as it produces a cold environment without creating moisture, which can damage sensitive items.

The other options highlight different substances that, while potentially confused with dry ice, do not accurately describe its composition. Frozen water is simply ice, liquid nitrogen is a cryogenic liquid used for cooling but is distinctly different from dry ice, and frozen oxygen is not a common state for that element and does not function as a refrigerant in the same manner. Thus, the defining characteristic of dry ice as solid carbon dioxide is what sets it apart and makes it the correct choice.