Final answer:
The question focuses on the internal controls related to purchasing processes, and the option about using prenumbered purchase requisitions matched with vendor invoices is the key for ensuring transaction completeness.
Step-by-step explanation:
The question regarding the completeness of purchasing transactions pertains to the internal controls within the purchasing process of a company. Among the options provided, B. Are prenumbered purchase requisitions used and are they subsequently matched with vendor invoices? would most likely be included in an internal control questionnaire to ensure that all purchasing transactions are complete. This option implies the use of a control procedure that helps in verifying that all issued requisitions result in corresponding purchase orders and eventually in invoices that are matched and recorded, thereby ensuring the completeness of the purchasing transactions.