The correct answer is B. Marginal utility.
Marginal utility is the additional satisfaction or benefit that a consumer gains from consuming one more unit of a good or service. It is calculated by taking the difference between the total utility from consuming two consecutive units of a good.
For example, if a consumer gets 10 units of utility from consuming one unit of a good and 12 units of utility from consuming two units of the good, then the marginal utility of the second unit is 2 units.
Marginal utility is important because it helps to explain how consumers make decisions about how much of a good or service to consume. In general, consumers will continue to consume a good until the marginal utility of consuming an additional unit is equal to or less than the marginal cost of consuming that unit.
The other options are incorrect for the following reasons:
- Total utility is the total satisfaction or benefit that a consumer gains from consuming all units of a good or service. It is calculated by adding up the marginal utilities of all units consumed.
- Additional utility is the difference between the total utility from consuming two consecutive units of a good. It is equal to the marginal utility of the second unit.
- Derived utility is the utility that a consumer derives from a good or service that is used to produce another good or service. For example, the utility that a consumer derives from a hammer is derived from the utility that the consumer derives from the nails that the hammer is used to drive.