Rusting of iron is caused by:

Rusting of iron is a chemical process that primarily involves oxidation. When iron comes into contact with moisture and oxygen from the environment, it undergoes a reaction where iron atoms lose electrons, resulting in the formation of iron oxide, commonly known as rust. This process is specifically an example of oxidation because it entails the combination of iron with oxygen in the presence of water or humidity.

Oxidation is characterized by the loss of electrons, and in the case of rusting, the iron reacts with oxygen, which leads to the corrosion of the metal over time. The presence of water acts as an electrolyte that facilitates this electrochemical reaction.

The other choices, while related to chemical processes, do not directly relate to the mechanism behind rusting. For instance, reduction involves gaining electrons, which is not what happens to iron during rusting. Evaporation and condensation refer to physical processes related to changes in state of matter and do not contribute to the chemical reaction of rust formation. Thus, the process of rusting is best understood as an oxidation reaction.