Low-carb fad decreases demand for high-carb food: equilibrium

This option suggests that an increase in price would lead to an increase in quantity sold, which contradicts the law of demand. Generally, as prices rise, the quantity demanded decreases, not increases. Therefore, this relationship does not apply in the context of decreased demand.

This choice implies that a decrease in price would lead to an increase in quantity sold. While a reduction in price could increase demand, the scenario indicates that demand for high-carb foods is already decreasing due to the low-carb fad. Thus, lowering prices would not necessarily increase the quantity sold, as the underlying demand is weak.

This option suggests that there would be no change in price or quantity, which is inaccurate given the significant shift in consumer preferences. The decrease in demand due to the low-carb trend would likely lead to observable changes in both price and quantity in the market for high-carb foods.