For Sales Returns,the Least Effective Control to Prevent Fraudulent Processing

For sales returns,the least effective control to prevent fraudulent processing of a credit memo is to

A) reconcile total of credit memos to total debits posted to customers' subsidiary ledgers.
B) require approval for each credit memo by the credit manager.
C) sequentially prenumber all credit memos and perform a sequence check at the end of each day.
D) match each credit memo with a receiving report.