Answer:
Option D Economies of Scale.
Step-by-step explanation:
The reason is that now he is able to control the costs due to his bulk production which brings economies of scale. This economies of scale is due to bulk production and increased bargaining power. The supplier don't want you to leave him and so restrain you to go he gives you additional benefits in the shape of bulk discounts. This bulk discounts helps you to keep the cost as low as possible and decrease the cost to add a competitive advantage to win the market. So the right option here is economies of scale.