Answer: C: being the bankers' bank.
Explanation:
The Fed is the Central Bank system of the United States. This means that they have certain duties conferred on them in order to ensure that the financial system of the country does not fail.
One of those duties is to be the Bankers' Bank. This means that the Fed can loan money to Commercial banks just like how Commercial banks do to entities. In acting as the lender of last resort and loaning money to banks so that they could survive the 2007 Financial crises, the Fed was acting as the Bank for the banks.
