Choice "D" is correct. When a material weakness exists, the auditor should issue an adverse opinion.
Choices "c" and "b" are incorrect. Failure of management to provide a written representation letter acknowledging its responsibility for the effectiveness of internal control generally will result in a disclaimer of opinion or withdrawal from the engagement.
Choice "a" is incorrect. While the auditor is required to communicate significant deficiencies to management and those charged with governance, the opinion on internal control need not be modified unless a material weakness is noted.
