Answer:
If this is a multiple choice, I'm afraid that we can only see the first option, which is A. A unit of account. I'm not sure if this is the complete answer. Nevertheless, here are the functions of money:
1. It acts as a rationing device, or basically a system of who gets what in an economy where goods/services are scarce or not enough to meet the demands of the consumer. Building off of that, it is a standard method of deferred payment within rationing devices. Non-rationing devices include bartering, first come, first serve policies, seniority, etc.
2. It is an agreed-upon medium of exchange of which transactions of most goods/services occur.
3. It is a store of value where the value of a currency is universally agreed upon and recognized.
Hope this helps!