What condition must be met for liquid water to evaporate into the atmosphere?

Liquid water evaporates into the atmosphere when there is sufficient space in the air for its molecules. This means that the air must not be fully saturated with water vapor; otherwise, the evaporation process cannot continue effectively. When water molecules at the surface of the liquid gain enough energy, typically from heat, they can transition into the gas phase and become water vapor. As this process occurs, the air must have available capacity to accommodate these new gas molecules; if the air is already saturated, the transition would be hindered.

In relation to the other options, while high temperatures and low humidity can enhance evaporation, they are not strict requirements for the process to occur. Dry air contributes to evaporation by facilitating the transition of liquid to vapor but is not a necessary condition in the same sense as having space in the air.