Which of the following statements is most correct?

The market turmoil in 2007 2008 was caused partly by banks lending to underqualified borrowers.

The mortgages held by investment banks during the financial crisis were considered to be toxic assets.

Contagion occurs when the failure of one financial institution leads to the failure of another.

The debt-to-GDP ratio is not a good measure of its debt burden. The total amount of debt that a country has is a more meaningful measure.

More than one of the answers is correct.