Answer:
d. more than one level of needs can operate simultaneously
Step-by-step explanation:
The ERG Theory of Motivation is a simple but a more flexible type of hierarchy of Needs given by Maslow.. It suggests three needs which must all be completed and satisfied for an individual to be motivated. This three needs for motivation are are growth, relatedness and existence. According to the ERG model of motivations, at same time one or more than one level can be simultaneously operated.
Hence the correct option is (d).