What Forces Combined in 2007 to Bring About the Worst

What forces combined in 2007 to bring about the worst economic downturn since the Great Depression of the 1930s?

A) Hurricane Katrina and the resulting bailout to homeowners
B) Bipartisan support of the wars in Iraq and Afghanistan
C) Predatory mortgage lending and irresponsible dealing on Wall Street
D) The election of the nation's first Black president and a Republican legislature