Which of the following could cause the supply of carrots to decrease? a. Consumers' incomes decrease. b. There is a technological advance in carrot production. c. The number of farmers growing carrots increases. d. Fertilizer costs increase.

The supply of a good is influenced by factors such as input costs, technology, and the number of sellers in the market. Let's analyze each option: a. **Consumers' incomes decrease.** - This affects **demand**, not supply. Lower incomes might reduce the quantity of carrots consumers are willing to buy, but it doesn't directly impact the supply side. b. **There is a technological advance in carrot production.** - Technological advancements typically **increase supply** by making production more efficient and reducing costs. c. **The number of farmers growing carrots increases.** - An increase in the number of producers in the market **increases supply**. d. **Fertilizer costs increase.** - Fertilizer is a key input in carrot production. If the cost of fertilizer rises, production becomes more expensive, leading to a **decrease in supply** as producers may supply less at the same price or require higher prices to maintain the same supply level. **Correct Answer:** **d. Fertilizer costs increase.**