Final answer:
The FDA report stating that vegetables enhance health leads to an increase in consumer preferences, causing the demand curve for vegetables to shift to the right, option d.
Step-by-step explanation:
When the U.S. Food and Drug Administration releases a report stating that eating vegetables enhances health and prolongs life, it influences the consumption behavior of individuals. This kind of information leads to an increase in consumer preferences for vegetables.
Consequently, more people are likely to want to purchase vegetables, leading to an increase in the quantity demanded at any given price. This change in preferences results in a shift to the right of the demand curve for vegetables because the change is related to the demand side of the market, not the supply side.
The increased number of farmers converting to organic farming, as mentioned in the reference material, also impacts the supply curve, causing it to shift to the right over time. However, the specific question concerns the effect of the FDA report, which is solely on the demand for vegetables.
Therefore, the correct option in response to the question, considering the information provided by the FDA report, is d. Demand curve shifts to the right.