To psychologists, motivation refers to __________.
a. a state of tension resulting from the deprivation of physical needs, such as those for food and water
b. a process in which an individual sets goals in order to increase his or her competence and skills
c. an inferred process within an organism that causes it to move toward a goal or away from an unpleasant situation
d. movement through a hierarchy of needs, beginning with survival needs for sleep, food, and water and reaching the need for self-actualization