Please provide a detailed explanation to the following question and explain why the other answer choices are wrong.

[18] An auditor noted that the accounts receivable department is separate from other accounting activities. Credit is approved by a separate credit department. Control accounts and subsidiary ledgers are balanced monthly. Similarly, accounts are aged monthly. The accounts receivable manager writes off delinquent accounts after 1 year, or sooner if a bankruptcy or other unusual circumstances are involved. Credit memoranda are prenumbered and must correlate with receiving reports. Which of the following areas could be viewed as an internal control deficiency of the above organization? A. Write-offs of delinquent accounts. B. Credit approvals. C. Monthly aging of receivables. D. Handling of credit memos