While studying in the library, Kayleigh became very hungry and went to a vending machine, which was empty, and to the cafeteria, which was closed. So she drove home and cooked herself a meal and ate it, satisfying her hunger. This food-seeking behavior was initiated by a bodily need with her search being sustained and directed to various food sources until her need was met. This illustrates

A) motivation.
B) behavioral dieting.
C) the opponent-process theory.
D) the Yerkes-Dodson law.