ZZZ Company employs batch processing for cash receipts. Customers repeatedly contact the company complaining that payments have not been credited to their account. Further investigation revealed that data entry clerks have unintentionally been applying payments to the wrong customer account numbers. Which of the following controls would not be helpful in preventing or detecting such errors? Select one: O a. Use of turnaround documents O b. Sequence check O c. Batch total reconciliation O d. Key verification O e. Redundant data check