Final answer:
When a check is drawn on Bank A and deposited in Bank B, Bank A's reserves decrease and Bank B's reserves increase, which affects the banks' abilities to make loans and potentially influences the overall money supply.
Step-by-step explanation:
When a check is drawn on Bank A and deposited in Bank B, there is an effect on the reserves of both banks. Bank A's reserves will decrease because it has to transfer funds to Bank B to cover the check. Conversely, Bank B's reserves will increase because it receives the funds from Bank A. However, it's important to remember that a bank must hold enough money in reserves to meet its liabilities. Should Bank A's reserves fall below the required reserve ratio, it may need to reduce its lending to restore its reserves to the required level, possibly leading to a decrease in the money supply.