Final answer:
An import quota shifts the supply curve to the left, causing a decrease in supply.
Step-by-step explanation:
When an import quota is imposed, it shifts the supply curve to the left, resulting in a decrease in supply. This is because the quota restricts the quantity of imported goods that can enter a country's market. As a result, the demand or supply of the product is shifted in the opposite direction of the curve that was affected. In this case, the supply curve shifts to the left, causing a decrease in supply.