Choice "C" is correct. PCAOB Auditing Standard No. 5 requires Jackson to perform an integrated audit, auditing both the financial statements and management's assessment of the effectiveness of internal control.
Choice "b" is incorrect. Jackson is required to perform an integrated audit, which includes an audit of internal control.
Choice "d" is incorrect. PCAOB Auditing Standard No. 5 requires Saffer to have an audit of internal control. Because the objectives and the work involved in an audit of internal control and in a financial statement audit are so closely related, the two audits must be performed together. Each of these two audits provides information that is relevant to the other.
Choice "a" is incorrect. An audit of internal control is required, regardless of the type of opinion rendered on the financial statements.