An internal auditor is testing cash disbursement transactions. Internal control policies require every check request to be accompanied by an approved voucher (that is, a package of documents evidencing that a good or service has been received and invoiced by the vendor). The voucher approval is based on a three way matching of a purchase order, receiving report, and vendor’s invoice. To determine whether checks have proper support, the internal auditor should begin her testing procedures by selecting items from the population of:
a. Check copies.
b. Purchase orders.
c. Receiving reports.
d. Approved vouchers.