Final answer:
A decrease in the price of imported resources explains a rightward shift in the aggregate supply curve because it reduces production costs, leading to an increase in supply.
Step-by-step explanation:
A rightward shift in the aggregate supply curve might best be explained by a decrease in the price of imported resources. This is because cheaper imports can reduce overall production costs for businesses, leading to an increase in supply. In contrast, options such as an increase in nominal wages (a), an increase in business taxes (b), and a decrease in productivity (c) would typically cause a leftward shift in the aggregate supply curve.
When the cost of inputs decreases, it is more affordable for firms to produce goods and services, which can be represented as a rightward or downward shift in the supply curve, indicating a greater quantity supplied at each price level. An improvement in technology or a decrease in resource costs both contribute to such a shift, enhancing the capacity to produce more efficiently and, thereby, the potential for growth in real GDP.