When forming an opinion on the adequacy of management's systems of internal control, which of the following findings would provide the most reliable assurance to the chief audit executive?

• During an audit of the hiring process in a law firm, it was discovered that potential employees' credentials were not always confirmed sufficiently. This process remained unchanged at the following audit.

• During an audit of the accounts payable department, auditors calculated that two percent of accounts were paid past due. This condition persisted at a follow up audit.

• During an audit of the vehicle fleet of a rental agency, it was determined that at any given time, eight percent of the vehicles were not operational. During the next audit, this figure had increased.

• During an audit of the cash handling process in a casino, internal audit discovered control deficiencies in the transfer process between the slot machines and the cash counting area. It was corrected immediately.