Final answer:
The 'additional pleasure or satisfaction from a good declines as more of it is consumed in a given period' defines Diminishing Marginal Utility.
Step-by-step explanation:
The definition provided corresponds to A) Diminishing Marginal Utility. This concept in economics describes the phenomenon where the satisfaction (or pleasure) a person gains from consuming each additional unit of a good decreases with every additional unit they consume in a certain period. An example of diminishing marginal utility is when someone consumes multiple ice cream cones; the first might provide great satisfaction, but by the fourth or fifth, the pleasure derived from each additional cone is likely much less than the first. This principle is critical in consumer behavior as it affects how much of a good a consumer is willing to buy and at what price.
The concept of diminishing marginal utility is different from the law of diminishing returns, which is applied more broadly across production in that more input does not necessarily mean proportionally more output. It can be studied through marginal analysis, where economic decisions are made based on incremental changes rather than whole changes. This does not directly relate to opportunity cost, which is the value of the next best alternative foregone as a result of making a decision.