Answer:
C. The demand for vegetables in the United States has increased.
Step-by-step explanation:
If many Americans have decided to adopt vegetarian diets and stopped eating meat, then the demand for meat would decrease. At the same time, the demand for vegetables would increase, as people are eating more vegetables and tofu instead of meat. This would lead to a shift in the market, with a decrease in the price of meat and an increase in the price of vegetables. As a result, the supply of meat would decrease as producers would be less willing to produce meat at a lower price, while the supply of vegetables would increase as producers would be more willing to produce vegetables at a higher price.