Option 1: When the central bank buys securities, it injects money into the banking system, increasing reserves.
Option 2: This would occur if the central bank sells securities, not purchases them.
Option 3: Increased money supply typically increases demand, not decreases it.
Option 4: Open market operations directly impact money supply, so it cannot remain unaffected.
Hence, Option 1: Increase the money supply in the economy -> When the central bank purchases government securities from commercial banks through Open Market Operations (OMO), it pays money to these banks. This increases the reserves held by commercial banks, which enhances their lending capacity. As banks lend more money, the money supply in the economy expands through the money multiplier effect. This is an expansionary monetary policy tool used to stimulate economic growth -> correct