which of the following causes of US subprime crisis 2007-2009 are regarded as self fullfilling which are fundamental? Give a brief reasoning?

causes of subprime crisis

1-Boom and Burst in housing market

2-Homeowner speculation

3-High-risk mortgage loans and lending/borrowing practices

4-Securitization practises

5-Inaccurate credit ratings

6-Government Regulation

7-Role of Fannie Mae and Freddie Mac

8-Financial institution debt levels and incentives