The correct answer is C
Money is the term which is described as something which serves as exchange medium, store of value and a unit of accounting. It is a exchange medium in the terms, that the person will agree to receive it by making a transaction.
In short, when depositing the money into any financial institution like banks, then this states the store of value function of the money.
Therefore, the one which is not the function of money is that it has the operations in the open market.