[填空题]The use of money has a long history. Money began very simply thousands of years ago when{{U}} (36) {{/U}}commodities such as metals, clam shells, stones, grain, and other things came into use as{{U}} (37) {{/U}}of exchange. instead of merely trading goods for goods, people began to exchange these early forms of "money" for goods. Commonly used metals were gold and silver. These metals were durable, easily{{U}} (38) {{/U}}, divisible, and uniform. About 600 B.C. coinage was invented. Metal, which had previously been used as money, was{{U}} (39) {{/U}}.It was cut into pieces of uniform weight and quality and was{{U}} (40) {{/U}}by the seal of the{{U}} (41) {{/U}}authority. Since coinage assured uniformity, buyers and sellers no longer had to weigh and test the metal for every transaction. Prices were still{{U}} (42) {{/U}}in terms of the amount of gold or silver one should offer or demand for other goods, but the new coinage form made the use of money much more convenie