What is the most important way the federal reserve ensures the United States money supply is safe and in circulation

Federal Reserve increases the money supply in the hands of the public if it buys back issued securities from large banks.

Explanation:

Federal Reserve increases the money supply in the hands of the public if it buys back issued securities from large banks. Conversely, Federal Reserve decreases the money supply in the hands of the public if it sells securities. As a result, the money supply increases.

Federal reserve provides and maintains an effective and efficient payment system. It also regulates banking operations.