The correct option is
B. A decrease in the price of a substitute good.
Detailed Explanation
To understand why option B is the correct answer, we need to delve into the concepts of demand, normal goods, and the relationships between goods in economics.
- Understanding Demand for Normal Goods:
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Normal goods are those for which demand increases when consumer income rises and decreases when consumer income falls. They are typically goods that people buy more of as they have more disposable income.
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Substitute Goods:
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Substitute goods are products that can replace each other. For example, if the price of coffee decreases, some consumers may choose to buy coffee instead of tea, which is a substitute for coffee. When the price of a substitute good falls, consumers are likely to buy more of that substitute and less of the original good.
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Analyzing Option B:
- If the price of a substitute good decreases, consumers will find the substitute more attractive due to its lower price. This leads to a decrease in the quantity demanded for the normal good because consumers will switch their consumption from the normal good to the now cheaper substitute. Therefore, a decrease in the price of a substitute good directly leads to a decrease in demand for the normal good.
Why the Other Options Are Incorrect
- Option A: An increase in consumer income:
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This option is incorrect because an increase in consumer income typically leads to an increase in demand for normal goods. As people have more money, they are more likely to purchase more of the normal good, not less.
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Option C: An increase in the price of a complementary good:
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Complementary goods are products that are often consumed together, such as printers and ink cartridges. If the price of a complementary good increases, the demand for the normal good is likely to decrease because the overall cost of consuming both goods rises. However, this scenario does not directly lead to a decrease in demand for the normal good itself; rather, it affects the quantity demanded due to the increased cost of the complementary good.
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Option D: A successful advertising campaign promoting the good:
- This option is also incorrect because a successful advertising campaign is designed to increase awareness and desirability of the good, which would likely lead to an increase in demand, not a decrease. Advertising aims to persuade consumers to buy more of the product.
Summary of Key Concepts
- Normal Goods: Demand increases with income and decreases with income drops.
- Substitute Goods: A decrease in the price of a substitute leads to a decrease in demand for the original good.
- Complementary Goods: An increase in the price of a complementary good can decrease the demand for the normal good but does not directly lead to a decrease in demand.
- Advertising: Effective advertising typically increases demand for the good being promoted.
Revision Summary
- Normal goods see increased demand with rising incomes.
- A decrease in the price of a substitute good leads to decreased demand for the original good.
- An increase in the price of a complementary good can reduce demand for the normal good.
- Successful advertising campaigns generally increase demand for the promoted good.