An entity's internal control requires for every check request that there be an approved voucher, supported by a prenumbered purchase order, and a prenumbered receiving report. To determine whether checks are being issued for unauthorized expenditures, an auditor most likely would select for testing from the population of:

	purchase orders.
	approved vouchers.
	canceled checks.
	receiving reports.

What are canceled checks ? And why is this answer the correct one, since approved vouchers are the document used to approve purchase orders