An internal auditor performed a test of controls and found that a statistically selected representative sample of recorded transactions within the account receivables ledger had an error rate that was within management expectations.The associated revenue account was outside the scope of the audit engagement.How should the conclusion to this engagement be reported?

a. The auditor should state that the error rate was within the selected confidence level

b. Negative assurance should be provided, as the associated revenue account was not examined

c. The auditor should state that controls over the recording of transactions in the revenue account are operating effectively

d. Positive assurance could be provided for the effectiveness of the accounts receivable controls