Answer: А. reduce the checkbook balance
Explanation:
The customer gave a check to Stear to settle their account for goods purchased from Stear. If the check is classified as Non-Sufficient Funds (NSF) check, it means that the bank of the customer did not send money to Stear's bank when Stear deposited the check because the customer did not have enough money in their account.
To correct this, reduce the cashbook balance by the amount on the check because the bank did not record the check because they never received the funds, but the business did in their cashbook.