Answer:
A. signing up for overdraft protection
Explanation:
Overdraft protection is an option that banks offer on checking accounts to avoid that a transaction would make that the balance fall below the minimum amount required. When people use this overdraft protection they have to link a savings account or a credit card and an amount will be taken from there to cover the shortfall. According to this, the answer is that Ann could have prevented the fee for going below the minimum balance by signing up for overdraft protection.