Final answer:
The correct answer is option c, that the participants liked their 'last' piece of chocolate better and found the whole experiment more enjoyable. This reflects the law of diminishing marginal utility, where each additional unit consumed has less added satisfaction.
Step-by-step explanation:
The answer to the question whether those told that their fifth and final piece of chocolate was their "last" piece liked it better and rated the whole experiment as more enjoyable than those told it was their "next" piece corresponds to the concept of the law of diminishing marginal utility. This economic principle suggests that as a consumer enjoys successive units of a good or service, the additional satisfaction gained from consuming one more unit tends to decrease. The enjoyment or utility gained from a 'last' chocolate piece could be perceived as higher because of the psychological effect that this is a final, therefore special, experience. Conversely, when told it is the 'next' piece, the implication is that the consumption is routine, thus the experience may not be savored to the same extent.