The law of diminishing marginal utility states:

1. Analyze the question You are asked what the law of diminishing marginal utility states.

2. Explain the concept

• Utility is the satisfaction a consumer gets from consuming a good.
• Marginal utility (MU) is the extra satisfaction from consuming one more unit.
• The law of diminishing marginal utility says that, as a consumer takes more and more units of a good within a given time, the extra satisfaction from each additional unit falls. This holds when other things stay the same.

3. Solution: check each option

• A. The supply curve slopes downward. This is wrong. Supply concerns producers, and the normal supply curve slopes upward (the law of supply). It has nothing to do with consumer satisfaction.
• B. Your utility grows at a slower and slower rate as you consume more and more units of a good. This is correct. Total utility still rises, but by smaller and smaller amounts, which means marginal utility is falling. This is the core idea of the law.
• C. The elasticity of demand is infinite. This is wrong. Infinite elasticity describes a perfectly elastic demand curve, which is a different concept.
• D. None of the above. This is wrong because B is correct.

Example: Suppose you are very hungry and eat plates of jollof rice.

• 1st plate: very satisfying (MU = 20)
• 2nd plate: still good (MU = 14)
• 3rd plate: less so (MU = 8)
• 4th plate: barely wanted (MU = 2)

Total utility climbs (20 → 34 → 42 → 44), but more slowly each time. That is exactly what option B describes.

4. Answer: The correct option is B.

5. Exam tip: Remember "more consumed, less extra satisfaction". If you see the words "additional unit" or "marginal" together with "falls" or "decreases", think diminishing marginal utility. In a graph, the MU curve slopes downward. Total utility is at its maximum when MU = 0.