Which of the following processes adds moisture to the air?

The process that adds moisture to the air is evaporation and sublimation.

Evaporation occurs when water transforms from a liquid state to a gas, thereby increasing the water vapor content in the atmosphere. This typically happens when water from oceans, lakes, rivers, or even soil heats up due to sunlight and rises into the air. As the water vapor accumulates, it contributes to humidity levels.

Sublimation, on the other hand, is the process by which ice or snow transitions directly into water vapor without first becoming liquid. This process also adds moisture directly to the air. This is particularly relevant in colder climates where snow or ice can sublimate, enhancing the humidity levels in the atmosphere.

The other options do not primarily relate to adding moisture to the air in this context. Condensation and precipitation primarily involve the processes of water vapor turning back into liquid form, while cooling and freezing would indicate changing from a vapor or liquid to a solid state, which would reduce moisture in the air. Filtration typically refers to the removal of particles and is unrelated to moisture content in the air.