Answer:
D An increase in raw material prices
Step-by-step explanation:
It can be concluded that the four other events have the positive effects on the aggregate supply. 1) An increase in immigration would lead to the higher demand for output and the higher supply in the market to serve the immigrants. 2) Investment in human capital would help enhance the productivity of firms, raise the capacity to supply. 3) A decrease in business tax would help firm reduce the cost of production, raising the resources for production to increase aggregate supply. 5) the introduction of technology contributes to the higher productivity of producers - raising the aggregate supply as well.
Reversely, the increase in material price raises the cost of production, decline the aggregate supply.