Which of the following best describes theory y? a. a theory of motivation describing five levels of human needs and arguing that basic needs must be fulfilled before people work to satisfy higher-level needs b. a theory of motivation holding that people are naturally responsible, growth oriented, self-motivated, and interested in being productive c. a theory of motivation holding that people are naturally irresponsible and uncooperative d. a theory of motivation holding that job satisfaction depends on two types of factors, hygiene and motivation