An internal auditor is testing cash disbursement transactions. Internal control policies require every check request to be accompanied by an approval 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 3-way matching of purchase order, receiving report, and vendors invoice. To determine whether checks have proper support, the internal auditor should begin her testing procedures by selecting items from the population of:\ \ \ Receiving reports\ \ \ Purchase orders\ \ \ Check copies \ \ \ Approved vouchers