Final answer:
Option d, a price floor will have the largest effect if it is set substantially below the equilibrium price.
Step-by-step explanation:
The most accurate statement is option d. A price floor will have the largest effect if it is set substantially below the equilibrium price. A price floor is a government-imposed minimum price that is set above the equilibrium price.
When the price floor is set substantially below the equilibrium price, it has a significant impact on the market. It creates a surplus, where the quantity supplied exceeds the quantity demanded, leading to excess supply. This surplus puts downward pressure on prices and can have a significant effect on reducing market activity.
In a demand and supply diagram, setting the price floor substantially below the equilibrium price would be shown as a horizontal line below the intersection of the demand and supply curves.