What is the chemical symbol for carbon dioxide?

The chemical symbol for carbon dioxide is represented as CO2. This notation indicates that each molecule of carbon dioxide consists of one carbon (C) atom and two oxygen (O) atoms. The subscript "2" in the formula signifies that there are two atoms of oxygen bonded with the single atom of carbon. This molecular composition is essential for understanding the behavior and reactions of carbon dioxide in various chemical processes and its role in biological systems, such as respiration and photosynthesis.

The other choices do not accurately represent carbon dioxide. For instance, CO refers to carbon monoxide, which consists of one carbon atom and one oxygen atom, while O2C and O2CO do not conform to any known chemical formulas in terms of representing carbon dioxide. Hence, CO2 is the definitive and correct representation for this compound.