The answer is the first one (or A): a debit memorandum that decreases the account balance.
Explanation for each option:
a. Debit memorandum that decreases the account balance: This is correct. An NSF (Non-Sufficient Funds) check is a check that cannot be processed because the account holder does not have enough funds in their account. When a bank processes an NSF check, it issues a debit memorandum to the account holder, indicating that the check amount is being deducted from their account balance, thus decreasing it.
b. Credit memorandum that increases the account balance: This is incorrect. A credit memorandum is used to increase the account balance, which is not the case with an NSF check.
c. Debit memorandum that increases the account balance: This is incorrect. A debit memorandum decreases the account balance, not increases it.
d. Credit memorandum that decreases the account balance: This is incorrect. A credit memorandum increases the account balance, not decreases it.
In summary, an NSF check results in a debit memorandum that decreases the account balance.