Final answer:
A bank service charge appears on a bank statement as a d. debit memorandum that decreases the account balance.
Step-by-step explanation:
When a bank service charge appears on a bank statement, it represents money that the bank has taken out of an account for the services it provides.
This type of transaction is known as a debit memorandum and it decreases the account balance because it is an amount that the bank has charged and thus removed from the account.
Therefore, the correct answer to what a bank service charge appears as on a bank statement is a d. debit memorandum that decreases the account balance.