__小题1:___ People use money to buy food, furniture, books, bicycles and hundreds of other things they need or want． When they work, they usually get paid in money．
Most of the money today is made of metal or paper．___小题2:___ 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．
The first metal coins were made in China．They were round and had a square hole in the centre． ___小题3:____
Different countries have used different metals and designs for their money．___小题4:___ Sweden and Russia used copper （铜） to make their money． Later some countries began to make coins of gold and silver．
But even gold and silver were inconvenient if you had to buy something expensive． Again the Chinese thought of a way to improve money．____小题5:_____The first paper money looked more like a note from one person to another than the paper money used today．
Money has had an interesting history from the days of shell money until today．
A．The first coins in England were made of tin （锡）．
B．But people used to use all kinds of things as money．
C．No one knows for certain when people began to use money．
D．People strung （串连） them together and carried them from place to place．E. Money, as we know, is all made of paper．
F. They began to use paper money．
G. Today anyone will accept money in exchange for goods and services．
时（T为交流的周期），原线圈中的电流瞬时值为0.03A．变压器的原、副线圈的匝数比为（ ）
：3