nancy is the auditor for chiomsys pharmaceuticals, a manufacturer of covid-19 vaccinations. the company has a complex pricing model where the price of the covid vaccination varies depending on the wealth of the purchasing nation. after evaluating the specific risks and circumstances of chiomsys, nancy decides on a combined audit approach. which of the following statements justifies nancy's choice of a combined approach?

a. The inherent risk around the accuracy of revenue recorded has increased but the controls are effective.

b. nancy tested a sample of invoices as part of a test of controls and concluded, based on the sample exception rate, that the controls around revenue were ineffective.

c. the CFO at chiomsys informed nancy that the new building system has major bugs that have not been fixed.

d. the controls around revenue and accounts receivable are ineffective.