Which of the following controls could be used to mitigate the threat of accepting unordered items?

		Use of flags in the ERP system to identify discrepancies between ordered and received quantities if the variance exceeds a preset threshold.
		Use of automation techniques like bar codes or RFID tags that can reduce errors in the receipt of goods process.
		Use of supplier audits and frequent reviews of receiving reports.
		Requiring existence of approved purchase orders prior to acceptance of any delivery.