Marginal utility is:

a. the change in a consumer's utility resulting from the addition of a very small amount of some good.
b. the total utility a resulting from consuming some good, divided by the amount consumed.
c. the change in a consumer's utility resulting from the addition of a very small amount of some good, divided by the amount added.
d. the change in a consumer's utility resulting from the addition of a very small amount of some good, divided by the total amount being consumed.