By the height of the housing bubble in 2005 and early 2006, lenders had greatly loosened the standards for obtaining a mortgage loan, with many mortgages being granted to sub-prime borrowers and "Alt-A" borrowers .

A. with flawed credit histories: who did not document their incomes

B. who borrowed more than 120 percent of the value of the house: with no proof of U. S. citizenship

C. who borrowed money at rates below the prime interest rate: who had AAA credit ratings

D. who purchased homes in depressed housing markets, who purchased homes which were repossessed by government agencies.