Service perishability means that ________.
a. evaluation of services is subjective and it changes from customer to customer
b. the quality of services depends on who provides them as well as when, where, and how they are provided
c. services cannot be stored for later sale or use
d. services cannot be seen, tasted, felt, heard, or smelled before they are bought
e. services cannot be separated from their providers, whether the providers are people or machines