A Large Difference in Temperature Between a Wet Bulb and a Dry

Multiple Choice

A large difference in temperature between a wet bulb and a dry bulb on a sling psychrometer indicates which of the following?

A) That the air is cooling by adiabatic expansion.
B) That the relative humidity is high.
C) That substantial evaporation is occurring from the wet bulb.
D) That substantial condensation is occurring on the wick.