Which of the Following Is NOT a Preventive Control

Which of the following is NOT a preventive control:

A) The general ledger master file is locked in a safe each night
B) All bills are marked "paid" to preclude duplicate payment
C) The accounts receivable subsidiary ledger is reconciled against the general ledger accounts receivable control account.
D) Only the credit manager may approve customers' credit sale orders
E) Customer numbers are verified by the computer before a sale order is accepted to ensure the sale order is from an established customer