资料题：From the passage we know that a person's thumbprint is（　）。

Someday in the future we may not need to have money in our pockets.Is life easier when people don't need to carry any coins or currency at all? ls money heavy to carry? Is it safe to carry money? Maybe in the future each of us will have only one small plastic credit card.We will use it to buy all the things we now buy with money.We will not need money to pay for things.Of course .we may still have some of the problems with cards that we now have with money.Sometimes we lose money.Maybe we will lose the card.People steal money.Maybe someone will sake the card.Someone may even make a card:that looks like our card.Since we can't buy anything without our card, the credit card may be no better than currency.Is there something even easier to use than credit cards? All of us have a thumbprint(拇指的指纹).No two thumbprints are the same.Maybe somebody in the government will keep people's thumbprints with a number.No person will have the same thumbprint or number.When we want to buy something we will put our thumbs on a machine or computer.Each store or business will have one.Everyone's thumbprint will be in the computers.It will be very difficult to lose our thumbprint.It will be difficult for someone to steal it or make one like it.