Barbara Beck, CPA is auditing accounts receivable and wants to determine whether "accounts receivable is stated at net realizable value". Which of the following audit procedures for accounts receivable best meets this objective?

a Vouch a sample of accounts receivable balances to the sales invoice

b Review loan agreements for indications of whether accounts receivable have been factored or pledged

c Review the aged accounts receivable trial balance for significant past due accounts

d Review the accounts receivable trial balance for the amounts due from employees and officers