The correct answer is: C. Buffer stock
A buffer stock is a stock of a product which is held by a trade body or government as a means of regulating the price of that product. It is used to prevent prices from fluctuating too much, which can be harmful to both producers and consumers.
A stock pile is a large quantity of goods that are stored in anticipation of future demand. It is often used by businesses to protect themselves against unexpected changes in the market.
A hoard stock is a stock of goods that is kept hidden or secret. It is often used by people who are trying to avoid taxes or regulations.
A withheld stock is a stock of goods that is not being sold. It is often used by businesses to try to increase the price of their products.