Which statement best exemplifies current motivation theories? Select one: a. Freud's psychodynamic theory of motivation has generally been supported with the strongest empirical evidence b. there are several approaches to motivation, and one or another may be useful in specific organizational contexts, with specific individuals or groups, at different times c the motivational models that make strong economic assumptions regarding human motivation have received the most universal acceptance d. the reinforcement approach to motivation has been found to be superior to other motivational models alth and den