Final answer:
The principal expenditures of NET R from a moist, nonvegetated surface are sensible heat and latent heat, transferred via radiation, evaporation, convection, and conduction.
Step-by-step explanation:
The principal expenditures of NET R from a moist, nonvegetated surface are primarily due to sensible heat and latent heat. Sensible heat is associated with the temperature change of the air or surface and can be transferred through processes such as convection and conduction. Latent heat is associated with phase changes of water such as evaporation and condensation. Heat can be exchanged by four mechanisms: radiation, evaporation, convection, and conduction.
Convection is the heat transfer due to the macroscopic movement of the fluid. Conduction is the heat transfer through a substance or between substances in contact without the movement of the material. The answer to the student's question involves understanding that heat is energy transferred solely due to a temperature difference and this can occur through various processes.