The correct answer is option 3: The solid-state of carbon dioxide.

Dry ice is the term used to describe the solid-state of carbon dioxide. Unlike regular ice, which is frozen water, dry ice is formed when carbon dioxide gas is cooled to a very low temperature and condenses into a solid without passing through a liquid phase. This process is called sublimation.

Dry ice gets its name because it does not melt like regular ice. Instead, it undergoes sublimation, which means it changes directly from a solid to a gas without becoming a liquid. This is why dry ice produces a smoky or foggy effect when it comes into contact with warmer air or liquids. It also remains extremely cold, with a temperature of around -78.5 degrees Celsius (-109.3 degrees Fahrenheit).

Dry ice is commonly used for several purposes, including as a cooling agent in the transport of perishable goods, for creating special effects in stage productions and movies, and for scientific experiments. It should be handled with care and in well-ventilated areas, as the release of carbon dioxide gas from dry ice can displace oxygen in confined spaces.