The correct answer is C. Wet-bulb temperature.
The wet-bulb temperature is the temperature of a thermometer whose bulb is covered with a wet cloth. The evaporation of water from the cloth cools the thermometer, and the wet-bulb temperature is always lower than the air temperature. The wet-bulb temperature is a measure of the humidity of the air. The higher the humidity, the lower the wet-bulb temperature.
The heat index is a measure of how hot it feels when the temperature and humidity are combined. The heat index is higher than the actual temperature when the humidity is high.
The minimum temperature is the lowest temperature that occurs during a 24-hour period.
The frost point is the temperature at which water vapor in the air condenses to form ice crystals.
The wind chill temperature is a measure of how cold it feels when the wind is blowing. The wind chill temperature is lower than the actual temperature when the wind is blowing.