Final answer:
To countermand a check drawn on a bank, the drawer must notify the bank in writing to cancel the check.
Step-by-step explanation:
A check drawn on a bank is an order to pay a sum of money and an authorization to charge the amount to the drawer's account. The drawer may countermand this order by notifying the bank in writing to cancel the check.
This means that the drawer informs the bank in writing to stop the payment on the check.
The other options, such as increasing the check amount, withdrawing additional funds from the account, or using the check for a different purpose, do not countermand the order to pay the specific sum of money and authorize the charge to the account.