Final answer:
The correct answer to the question is 'a. Marginal benefit'. Marginal benefit represents the extra utility a consumer gets from the consumption of one additional unit of a good or service, crucial in rational decision-making.
Step-by-step explanation:
The extra benefit associated with producing or consuming the next unit is called the marginal benefit. Economic concepts like marginal benefit are part of marginal analysis, which plays a crucial role in decision-making. For instance, as a consumer purchases more of a good, such as bus tickets, the utility derived from each additional ticket tends to decrease; this is known as the law of diminishing marginal utility.
As a rational consumer, Alphonso will compare the marginal utility he receives from each additional bus ticket to the opportunity cost, which in the given example is represented by the marginal utility of the foregone burgers. When these two measures equate, the consumer will stop purchasing additional units.
In contrast, the marginal cost refers to the cost of producing one more unit of a good, and sunk costs are past costs that can no longer be recovered and should not affect current economic decisions. Thus, it is the marginal benefit that describes the extra utility or satisfaction one gets from acquiring or consuming an additional unit of a good or service.