Choice "A" is correct. Unusual nonrecurring transactions near year-end are characteristic of related party transactions. Since related party transactions are not at arm's-length, management may use such transactions to bolster sales or assets.
Choice "d" is incorrect. Retesting ineffective controls would not assist the auditor in identifying related party transactions.
Choice "b" is incorrect. Confirmation of accounts receivable would not assist the auditor in identifying related party transactions.
Choice "c" is incorrect. Finding unrecorded contingent liabilities would not assist the auditor in identifying related party transactions.