Just before the collapse of the subprime mortgago market in 2007 the most important credit-rating agencies rated mortgage-backed securities with Aaa and AAA ratings Explain how it was possible that a few months into 2008, the same securities had the lowest possible ratings OA. As inflation soared in early 2008, returns on mortgage-backed securities was wiped out. Many AAArated products had to be downgraded to junk status B. When housing prices began to fall and subprime mortgages began to default, many AAA-rated products had to be downgraded over and over again C. The government revoked tax exemption to investors for these securities, thereby lowering returns and ratings