A Consumer Is Said to Be in Equilibrium in His

A consumer is said to be in equilibrium in his or her choice between two goods A and B when:

A) the total purchase of good A gives the same satisfaction as the total purchase of good B.
B) the last unit of good A purchased gives the same addition to satisfaction as the last unit of good b purchased.
C) each penny spent on good A gives the same satisfaction as each penny spent on good B.
D) the last penny spent on good A gives the same addition to satisfaction as the last penny spent on good B.
E) the last pennies spent on goods A and B generate no additions to satisfaction.