Which process is described as exothermic, self-sustaining, and can occur in an inert atmosphere?

The described process that is exothermic, self-sustaining, and capable of occurring in an inert atmosphere is combustion.

Combustion refers to a chemical reaction that typically involves the rapid oxidation of a fuel, resulting in the release of heat and light. This process is inherently exothermic, meaning it releases energy, primarily in the form of heat. Once initiated, combustion can sustain itself as long as there is a sufficient supply of fuel and the conditions for the reaction are maintained.

Interestingly, while combustion usually requires oxygen to occur, specific types of combustion, such as oxidizer-rich combustion or reactions with certain metal powders, can occur in inert atmospheres where typical oxygen sources are not present. The key aspect of combustion is that it can continue autonomously after the initial energy input is provided, allowing it to be self-sustaining.

The other processes listed do not meet all the criteria set out in the question. Evaporation and condensation are phase change processes involving the transition between liquid and gas states and do not primarily involve chemical reactions or significant energy release. Oxidation is a broader term that refers to any reaction where a substance loses electrons, and while it can be exothermic, it doesn't inherently imply self-sustainability