During the Economic Downturn of 2008-2009, the Federal Reserve

During the economic downturn of 2008-2009, the Federal Reserve

A) used open-market operations to purchase mortgages and corporate debt, just as it frequently does even when the economy is functioning normally.
B) took the unusual step of using open-market operations to purchase mortgages and corporate debt.
C) explicitly set its target rate of inflation at zero.
D) explicitly set its target rate of inflation well above zero.