People use money to buy food, furniture, books, bicycles and hundreds of other things they need or want. Most of the money today is made of metal or paper. But people used to use all kinds of things as money. One of the first kinds of money was shells. Shells were not the only things used as money. In China, cloth and knives were used. In the Philippine Islands, rice was used as money for a long time. Elephant tusks, monkey tails, and salt were used as money in parts of Africa. Some animals were used as money too. The first metal coins were made in China. They were round and had a square hole in the center. People _ them together and carried them from place to place. The first coins in England were made of tin  . Sweden and Russia used copper   to make their money. Later countries began to make coins of gold and silver. Later the Chinese thought of a way to improve money. They began to use paper money. Money has had an interesting history from the days of shell money until today. The word "strung" in the passage probably means_."
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