Correct Option: D. Decrease Explanation of the Correct Answer Marginal Utility Concept: Marginal utility refers to the additional satisfaction or benefit that a consumer derives from consuming one more unit of a good or service. In the context of beer consumption, as a drinker consumes more beers, the additional satisfaction gained from each subsequent beer tends to decrease. This phenomenon is rooted in the principle of diminishing marginal utility. Diminishing Marginal Utility: The law of diminishing marginal utility states that as a person consumes more units of a good, the utility (satisfaction) gained from each additional unit will eventually decline. For example, the first beer might provide a high level of satisfaction because it quenches thirst and provides enjoyment. However, as the drinker continues to consume more beers, the additional satisfaction from each subsequent beer decreases. This is because the drinker may become less thirsty, or the effects of alcohol may lead to saturation. Step-by-Step Breakdown: 1. Initial Consumption: When a drinker has their first beer, they experience a high level of satisfaction (high marginal utility). 2. Subsequent Consumption: As they drink a second, third, or fourth beer, the additional satisfaction from each beer diminishes. The second beer may still be enjoyable, but not as much as the first. 3. Saturation Point: Eventually, the drinker may reach a point where additional beers provide little to no additional satisfaction, or even negative satisfaction (discomfort or nausea). 4. Conclusion: Therefore, as consumption increases, the marginal utility of each additional beer decreases, leading us to conclude that the correct answer is D. Explanation of Incorrect Options

• A. Increase: This option suggests that as more beer is consumed, the satisfaction from each additional beer increases. This contradicts the principle of diminishing marginal utility, as it is generally observed that the more one consumes, the less satisfaction they derive from each additional unit.
• B. Remain constant: This option implies that the satisfaction from each additional beer does not change regardless of how many beers are consumed. This is also incorrect because, in reality, the satisfaction does change as consumption increases, typically decreasing.
• C. Fluctuate: While it is possible for marginal utility to vary in some contexts, the general trend for most goods, including beer, is a decrease in marginal utility with increased consumption. Fluctuation suggests that there could be random increases and decreases in satisfaction, which is not the typical behavior observed in the context of diminishing marginal utility.

Common Pitfalls

• Confusing Total Utility with Marginal Utility: Total utility can increase with more consumption, but marginal utility specifically refers to the change in satisfaction from consuming one more unit.
• Ignoring Individual Differences: While the law of diminishing marginal utility applies broadly, individual preferences and tolerances can vary. However, the general trend remains that marginal utility decreases with increased consumption.

Revision Summary

• Marginal utility is the additional satisfaction from consuming one more unit of a good.
• The law of diminishing marginal utility states that as consumption increases, the additional satisfaction from each unit decreases.
• The correct answer to the question is D: Decrease, as the marginal utility of beer declines with increased consumption.
• Understanding the difference between total utility and marginal utility is crucial for applying these concepts correctly.