Final answer:
The characteristic of money that allows people to postpone purchases is the 'store of value' feature, which ensures that money can maintain its value over time, allowing for savings and delayed spending, unlike perishable goods.
Step-by-step explanation:
The characteristic of money that allows people to postpone purchases and save their money to do so is the store of value attribute.
This means that money has the ability to maintain its value over time. One can hold onto money without the worry of it losing its significance the next day or the next year, even though in an economy with inflation, money might lose some buying power. This differs from bartering goods like shoes, which can go out of style and lose their worth. Therefore, the answer to the question which characteristic allows for postponing purchases is d) Store of value.
Furthermore, money as a standard of deferred payment is associated with this ability to delay use, as it can be accepted for transactions in the present that will be paid for in the future. Together, these functionalities of money enable it to act as both a medium of exchange and a robust method for saving and deferring payments over time.