What are the two main purposes of air washers?

Air washers are specifically designed to clean and pre-cool air, making option B the correct choice. The primary function of an air washer is to pass air through water, effectively capturing dust, airborne particles, and other contaminants. This process not only cleans the air but also aids in lowering its temperature, providing a more comfortable environment.

Furthermore, the interaction of air with water in an air washer can also increase humidity in dry conditions, which enhances comfort within the space. While other options mention relevant functions related to air management, they do not fully encapsulate the main purposes of an air washer as effectively as the cleaning and pre-cooling aspect does.

For instance, heat recovery and humidity control might be more associated with different HVAC systems like heat exchangers or humidifiers, rather than the specific functions of an air washer. Fresh air intake and exhaust are typically functions seen in ventilation systems, and dehumidification and filtration are more related to dehumidifiers and air purifiers, respectively. The focused purpose of air washers is clearly represented in the choice regarding their role in cleaning and pre-cooling air.