Answer: Bulk purchasing is correct answer.
Explanation:
Since we know that Buying items in larger volume is also known as "Bulk purchasing".
As Bulk purchasing is defined as the items which are purchased in larger volume.
It is the purchase of larger quantities than the usual as it is cheaper than purchasing a lesser quantity for a unit price.
In case of bulk purchasing, consumer pay a lower price per unit in exchange for buying much larger quantities. As it does with the wholesaler directly, or indirectly.
Hence, Bulk purchasing is correct answer.