Which of the following statements is true because of the law of diminishing marginal utility?

a.When a customer continues to eat more pie at the Pie Palace, each additional piece of pie gives a larger amount of marginal utility.
b.When a customer continues to eat more pie at the Pie Palace, each additional piece of pie gives a smaller amount of marginal utility.
c.The marginal utility of a piece of pie is maximum when the total utility of pie is zero.
d.The total utility of pie is at a maximum while the marginal utility of pie is still increasing.