Which of the following phrases or sentences in the independent auditor's report is improperly stated?

a. Those standards require that we plan and perform the audit to obtain assurance about whether the financial statements are free of material misstatement.

b. An audit includes examining, on a test basis, . .

c. In our opinion, the financial statements referred to above present fairly, in all material respects, . .

d. We conducted our audit in accordance with generally accepted auditing standards.