Explanation:

- Central Bank: The central bank regulates the money supply by controlling interest rates and issuing currency. It is the primary institution responsible for the monetary policy of a country.

- Commercial Banks: These banks create money by issuing loans to borrowers. When they provide loans, they increase the money supply through the creation of deposits.

- Both a) and b): Central banks and commercial banks together influence the money supply. While the central bank controls monetary policy, commercial banks expand the money supply through lending activities.

- Government: Although the government influences fiscal policy, it does not directly control the money supply. It primarily raises funds through taxes and borrowing.