What is wet-bulb temperature?

• A. tTemperature of air measured by thermometer whose bulb is dry.
• B. tIt is the temperature attained by small amount of evaporating water in such a manner that sensible heat transferred from air to liquid is equal to latent heat required for evaporation.
• C. tThe ratio of partial pressure of water vapor in air to the vapor pressure of water at same temperature.
• D. tDirect measure of moisture content in a gas