Which of the following statements best gives the reasons that a data usage bill for a smart phone is an essential (variable) expense? a. it is an obligation to pay, but the spender has some control over its amount. b. it cannot be eliminated in a later budget, in order to save money. c. it is expected to be the same amount every month. d. bills for services rendered have a higher priority than any other type of expense. select the best answer from the choices provided a b c d