根据短文内容回答下列问题：

　　The world has a big headache and it's caused by money．It began in America two years ago and it's traveled around the world by the speed of the Internet．

　　In just a few short months, billions and billions of dollars have disappeared．They just vanished into thin air．How can this be? Well, to understand that, you have to understand the idea of“value”．The“value”of something is what someone is willing to pay for it．That's easy when it comes to buying a bottle of green tea．You wouldn't pay more than a few yuan．But what about something like a house?

　　In America, houses are expensive．People have to get loans(贷款)in order to buy them．To get a loan you have to have a good job so the lender knows you're going to pay the money back．But American banks started making it easier for people to get loans．That meant more people could buy houses．More and more people want houses so their prices went up and people had to get bigger loans to buy them．Of course, many of these people couldn't afford(提供)to pay back the bigger loans, so the banks couldn't get their money back, the prices of houses went down and all that“value”disappeared．

　　Now the banks are out of money and governments around the world have had to step in and save them．

　　What does this all mean? Well, with the banks in trouble there is less money to invest(投资)and less money for people to buy things．That means less business, fewer jobs and more unemployment．It's a big headache for everyone and aspirin can't cure it．

1．What is the headache of the world caused by?

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2．When and where did the headache start?

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3．Billions and billions of dollars have disappeared into thin air, haven't they?

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4．What do Americans do when they want to buy houses?

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5．Why did banks start making it easier for people to get loans?

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6．Why couldn't the banks get their money back now?

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7．What do you think many Americans feel now with the banks in trouble?

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