Concept:Marginal utility measures the extra satisfaction gained from consuming one additional unit of a good or service.Explanation:Utility refers to the satisfaction a consumer receives from using a product.Total utility is the overall satisfaction from all units consumed.Average utility is the satisfaction per unit of the good consumed.Marginal utility is the change in total utility when consumption increases or decreases by one unit.Therefore, the rate of increase in utility is captured by the extra utility added by each additional unit.This extra utility is known as marginal utility.Answer:D. Marginal utility