Concept:The negative slope of the demand curve arises from the consumer's diminishing marginal utility, which causes quantity demanded to rise as price falls.
Explanation:According to the law of diminishing marginal utility, as a consumer consumes more units of a good, the extra satisfaction (marginal utility) from each additional unit decreases.
Because each extra unit gives less satisfaction, the consumer is willing to pay a lower price for additional units.
Thus, a lower price attracts a larger quantity demanded, while a higher price reduces quantity demanded.
This inverse relationship between price and quantity demanded gives the demand curve its downward (negative) slope.
Therefore, it is diminishing marginal utility, not diminishing returns, that best explains the negative slope of the demand curve.
Answer:D. diminishing marginal utility.