Answer:
B. maintain reserves
Step-by-step explanation:
The Federal Reserve expects commercial banks to retain a percentage of customers' deposits in their custody at all times. The amount retained in custody is known as reserves. It means the banks cannot loan out that reserve amount. It should be kept in the bank's vaults or with the Federal Reserve.
The reserve caters to the regular and unexpected withdrawals. The Federal Reserve determines the percentage to be retained as reserves. The reserve requirement is also a monetary policy tool for the Federal Reserve.