[12] An independent external auditor may use internal auditors to assist in the audit of accounts receivable. Of the following procedures, the one that would be most appropriate for the intemal auditors to perform is the A. Assessment of control risk for accounts receivable. B. Determination of the number of positive confirmation requests to be mailed to substantiate the existence of accounts receivable C. Preparation of an aged trial balance of accounts receivable. D. Establishment of the dollar amount of accounts receivable that is considered material