Dry ice is the common name for solid carbon dioxide (CO2) at temperatures below -78.5 degrees Celsius (-109.3 degrees Fahrenheit). It is called "dry" ice because it does not melt into a liquid like regular ice, but instead undergoes a process called sublimation, where it goes directly from a solid to a gas.

Option 1, solid carbon dioxide, is the correct answer. Solid CO2 is known as dry ice because it does not leave behind any liquid residue when it sublimates. It is often used as a cooling agent because it has a very low temperature, making it useful for preserving perishable items or creating smoke effects in entertainment productions.

Options 2, 3, and 4 are incorrect. Liquid carbon dioxide (option 2) is not called dry ice since it is in a liquid state, not solid. Similarly, liquid nitrogen (option 3) and liquid ammonia (option 4) are different substances and do not have the same properties as dry ice.

Therefore, the correct answer is option 1, solid carbon dioxide.