Which of the following questions would most likely be included in an internal control questionnaire concerning the completeness assertion for purchases?

a. Is an authorized purchase order required before the receiving department can accept a shipment or the vouchers payable department can record a voucher?

b. Are purchase requisitions prenumbered and independently matched with vendor invoices?

c. Is the unpaid voucher file periodically reconciled with inventory records by an employee who does not have access to purchase requisitions?

d. Are purchase orders, receiving reports, and vouchers prenumbered and periodically accounted for?