Law of Diminishing Marginal Utility

Steps:

• Recall that a demand curve shows quantity demanded increasing as price falls.
• Recognize the downward slope reflects consumers' willingness to buy more at lower prices.
• Link this to utility: as consumption rises, marginal utility falls, reducing willingness to pay high prices.
• Match to options: select the one explaining falling marginal utility.

Why A is correct:

• It states the law of diminishing marginal utility, where marginal utility (additional satisfaction) decreases with more consumption, so consumers demand more only at lower prices.

Why the others are wrong:

• B: Finite income explains budget constraints but not the core reason for the downward slope.
• C: Identical to A, so redundant; question likely has a duplication error.
• D: Describes producer pricing (supply curve), not consumer demand behavior.

Final answer: A