Which of the following is not a basic principle described by the AICPA related to audit reporting?

a. The auditor must state if the financial statements are in full compliance with GAAP.

b. The auditor can state that an opinion cannot be expressed.

c. The auditor can express an opinion that the financial statements are free of material misstatements.

d. By expressing an opinion on the financial statements the degree of confidence that users can place in the statements is enhanced.