my question is about impact of low interest rates on monetary policy

My question is written below and the only requirement is that it has to be 150 words. Thank you!

Since the end of the Great Recession, interest rates have been at historic lows—in some cases, close to zero. How is expansionary monetary policy, or more specifically a open market purchase, supposed to work? How do near-zero interest rates limit the ability of expansionary monetary policy to work?

How has the Fed responded to this quandary? That is, what policies has the Fed conducted?

In your opinion, how effective has the Fed’s policy been as a response to the Great Recession? What evidence can you suggest to support your position?