After multiple attempts, an auditor is unable to obtain a response for several positive requests for year$-$end accounts receivable confirmations. An appropriate alternative procedure to verify the existence of accounts receivable is:

a$.$ Visit the customer selected for confirmation and review documents in their possession.

b$.$ Obtain the aging of accounts receivable and trace it to the general ledger control account.

c$.$ Examine the applicable sales order, shipping document, and subsequent cash receipts.

d$.$ Examine subsequent cash disbursements and related receiving reports.