Correct Option: C. Decrease Explanation of the Correct Answer The concept of diminishing marginal utility is a fundamental principle in economics that describes how the satisfaction (or utility) a consumer derives from consuming additional units of a good changes as they consume more of it.

1. Understanding Utility:
2. Utility refers to the satisfaction or pleasure that a consumer derives from consuming goods and services.
3. Marginal utility is the additional satisfaction gained from consuming one more unit of a good.
4. Diminishing Marginal Utility:
5. The principle of diminishing marginal utility states that as a consumer consumes more units of a good, the additional satisfaction (marginal utility) gained from each subsequent unit will eventually decrease.
6. For example, consider a person eating slices of pizza. The first slice may provide a high level of satisfaction (high marginal utility), the second slice may still be enjoyable but less so than the first, and by the third or fourth slice, the satisfaction gained from each additional slice may be significantly lower.
7. Graphical Representation:
8. If we were to graph this concept, the x-axis would represent the quantity of the good consumed, and the y-axis would represent the marginal utility.
9. The curve would start high and slope downward, indicating that as quantity increases, marginal utility decreases.
10. Why Diminishing Marginal Utility Occurs:
11. This phenomenon occurs because consumers have limited wants and needs. As they satisfy their needs with more of a good, the additional satisfaction from consuming more of that good diminishes.
12. Additionally, as a consumer fills up on a good, they may start to prefer variety or different goods, leading to a decrease in the utility derived from additional units of the same good.

Explanation of Why Other Options Are Incorrect

• Option A: Increase indefinitely:
• This option suggests that as consumption increases, the additional satisfaction continues to rise without limit. This contradicts the principle of diminishing marginal utility, as it implies that consumers would always find more satisfaction in consuming more of the same good, which is unrealistic.
• Option B: Remain constant:
• If marginal utility remained constant, it would imply that each additional unit consumed provides the same level of satisfaction as the previous one. This does not reflect real consumer behavior, where satisfaction typically decreases as more of the same good is consumed.
• Option D: Become negative:
• While it is possible for marginal utility to become negative (indicating that consuming more of a good could lead to dissatisfaction), this is not a necessary outcome of the diminishing marginal utility principle. Diminishing marginal utility primarily indicates a decrease in satisfaction, not necessarily a transition to negative satisfaction. Negative marginal utility is more extreme and occurs in specific situations, such as overconsumption leading to discomfort.

Common Pitfalls

• Confusing Marginal Utility with Total Utility: Remember that while total utility can increase with more consumption, marginal utility specifically refers to the change in satisfaction from consuming one additional unit.
• Assuming Diminishing Marginal Utility Applies to All Goods: While this principle is widely applicable, there are exceptions, such as addictive goods where initial consumption may lead to increasing satisfaction until a certain point.

Revision Summary

• Diminishing marginal utility indicates that additional satisfaction from consuming more of a good decreases as consumption increases.
• The first units of consumption provide higher satisfaction, while subsequent units yield lower satisfaction.
• This principle is crucial for understanding consumer choices and demand in economics.
• Remember the distinction between marginal utility and total utility, and be aware of exceptions to the rule.