单项选择题

Passage One
There are still parts of the world today where coins and notes are of no use. People will buy nothing, and a traveler might starve if he had none of the particular local "money" to exchange for food. Among isolated peoples, who are not often reached by traders from outside, commerce usually means barter. There is a direct exchange of goods. Perhaps it is fish for vegetables, meat for grain, or various kinds of food in exchange for pots, baskets, or other manufactured goods. For this kind of simple trading, money is not needed, but there is often something that everyone wants and everybody can use, such as salt to flavor food, shells for ornaments, or iron and copper to make into tools and vessels.
These things-salt, shells or metals-are still used as money in out-of-the-way parts of the world today. Salt may seem rather a strange substance to use as money, as in countries where food of the people is mainly vegetable, it is often an absolute necessity. Cakes of salt, stamped to show their value, were used as money in Tibet until recent times, and cakes of salt will still buy goods in Borneo and parts of Africa. Metal, valued by weight, and preceded coins in many parts of the world. Iron, in lumps, bars or rings is still used in many countries instead of money. It can either be exchanged for goods, or made into tools, weapons or ornaments.
The early money of China, apart from shell, was of bronze, often in flat, round pieces with a hole in the middle, called "cash". The earliest of these are between three thousand and four thousand years old-older than the earliest coins of the eastern Mediterranean. ①Nowadays, coins and notes have taken the place of all the more picturesque forms of money, and although in one or two of the more remote countries people still hoard(储藏) it for future use on ceremonial occasions such as weddings and funerals, examples of primitive money will soon be found only in museums.
Primitive types of money are sometimes used______