Which of the following is a common method to control humidity in a building?

A dehumidifier is a common method to control humidity in a building because its primary function is to remove excess moisture from the air. High humidity levels can lead to discomfort, mold growth, and other issues, making it necessary to maintain a balanced and appropriate indoor humidity level.

The dehumidifier works by drawing in moist air, cooling it to condense the water vapor, and then releasing drier air back into the environment. This mechanism effectively lowers the humidity, making the indoor air more comfortable and reducing the risk of mold and mildew.

While other options do play roles in temperature and air circulation, they do not specifically target humidity control in the same way a dehumidifier does. For instance, a humidifier adds moisture to the air, which would not help in reducing humidity. Air conditioners can lower humidity levels indirectly by cooling the air, but they are primarily designed to lower temperature. Ceiling fans circulate air but do not directly affect humidity levels, making dehumidifiers the most efficient and effective choice for controlling humidity.