Which of the Following Would Provide the Greatest Assurance of the Accuracy

Which of the following would provide the greatest assurance of the accuracy of a computer program's computation of freight charges for catalog sales?

A) Use discovery sampling, selecting transactions from invoices which should have freight charges added to them.
B) Use either test data or parallel simulation to test the computer application.
C) Use difference estimation, selecting transactions from invoices which should have freight charges added to them.
D) Use generalized audit software to select a monetary-unit sample of invoices that have been billed to customers.