Final answer:
Alternative procedures in positive confirmations are required for unreturned confirmations in auditing. Examining shipping documents to verify shipment is not an alternative procedure for confirmations. The other options, sending a second confirmation request, examining subsequent cash receipts, and examining purchase orders and sales invoices, are considered alternative procedures.
Step-by-step explanation:
When positive confirmations are used in auditing, alternative procedures are required for unreturned confirmations. Alternative procedures should provide evidence about the existence and completeness of the receivables. Examining shipping documents to verify the shipment of merchandise (option C) would not be considered an alternative procedure as it does not provide direct evidence about the existence of receivables or their completeness. The other options, sending a second confirmation request (option A), examining subsequent cash receipts (option B), and examining purchase orders and sales invoices (option D), all provide direct evidence of the existence and completeness of receivables.