Which of the following is the best explanation as to why the Fed changed its approach to monetary policy after the 2007 - 2009 financial crisis?

Multiple Choice

Changes in the Fed Funds rate no longer influenced other rates in the economy.

Reserves had been depleted by the crisis, so banks could no longer borrow from other banks in the Fed Funds market.

The quantitative easing pursued by the Fed to combat the crasis and the ensuing recession had so diminished the assets on the Fed's balance sheet that it could no longer undertake traditional policy.

Reserves in the banking system had ballooned during the crisis to such an extent that traditional open market operations were no longer effective in raising or lowering the Fed Funds rate.