Correct option is B
Frost forms on the evaporator coils when the surface temperature of the coils is below the dew point and also below the freezing point of water. This typically happens when the system operates at low temperatures (e.g., in freezers) or when there is high humidity.
Frost acts as an insulating layer on the coils. Since ice/frost has low thermal conductivity, it reduces the heat transfer rate between the air and the refrigerant inside the coils. This decreases the efficiency of the evaporator.
Frost buildup can eventually block airflow through the coils, further reducing heat transfer and causing the system to work harder, leading to potential damage.
