根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。　　China has been the birthplace of many of the world's greatest inventions. It was, for example, the first country to produce paper money. Before the invention of paper money and coins, people used many different kinds of things for buying and selling. . This exchange of goods and services for other goods and services is called bartering.　　The next development was in 1000 BC, when China started making bronze and copper shells. It wasn't long before the Chinese made round coins out of metal. A. People also began collecting foreign coins as souvenirs.B. During that time, for example, buying a chicken might cost several potatoes.C. It was still many years before paper currency appeared in Europe.D. However, as economies developed, such exchanges became impractical.E. They also used tiny shells as money for buying and selling.F. As time went by, trade between countries increased.G. The first coins often had holes in them so that people could string them together.A. People also began collecting foreign coins as souvenirs.B. During that time, for example, buying a chicken might cost several potatoes.C. It was still many years before paper currency appeared in Europe.D. However, as economies developed, such exchanges became impractical.E. They also used tiny shells as money for buying and selling.F. As time went by, trade between countries increased.G. The first coins often had holes in them so that people could string them together.A. People also began collecting foreign coins as souvenirs.B. During that time, for example, buying a chicken might cost several potatoes.C. It was still many years before paper currency appeared in Europe.D. However, as economies developed, such exchanges became impractical.E. They also used tiny shells as money for buying and selling.F. As time went by, trade between countries increased.G. The first coins often had holes in them so that people could string them together.A. People also began collecting foreign coins as souvenirs.B. During that time, for example, buying a chicken might cost several potatoes.C. It was still many years before paper currency appeared in Europe.D. However, as economies developed, such exchanges became impractical.E. They also used tiny shells as money for buying and selling.F. As time went by, trade between countries increased.G. The first coins often had holes in them so that people could string them together.A. People also began collecting foreign coins as souvenirs.B. During that time, for example, buying a chicken might cost several potatoes.C. It was still many years before paper currency appeared in Europe.D. However, as economies developed, such exchanges became impractical.E. They also used tiny shells as money for buying and selling.F. As time went by, trade between countries increased.G. The first coins often had holes in them so that people could string them together.