它兩年前始於美國，很快便席卷全球。它應該指的是經融危機
2:The value of something is what someone is willing to pay for it.
事物的價值就是人們願意花多少錢買它。
3:To get a loan,you have to have a good job so the lender knows you're going to pay the money back.
想要貸款，妳必須有壹份好的工作，這樣貸方才知道妳會還錢。
4:The demand for houses increased their "value",so their price went up and people had to get bigger loans to buy them.
對房屋的需求增加了它們的“價值”，所以房價上漲了，而人們必須貸更多的款去買它們。
5:As a result,the banks couldn't get their money back.
結果，銀行就收不回自己的錢了。