Final answer:
A shift to the left of the supply curve on the graph indicates a decrease in supply, resulting in a higher equilibrium price and a lower equilibrium quantity.
Step-by-step explanation:
In this graph, a shift to the left of the supply curve would indicate a decrease in supply. This means that less of the product is available in the market, leading to a decrease in the equilibrium quantity and an increase in the equilibrium price. A shift to the left of the supply curve on the graph indicates a decrease in supply, resulting in a higher equilibrium price and a lower equilibrium quantity.
For example, if there is a decrease in the availability of raw materials needed to produce the product, suppliers may be able to produce less of the product, resulting in a decrease in supply.
Therefore, the correct answer is A) a decrease in supply.