Choice "D" is correct. The provision of services involving contingent fee arrangements impairs the auditor's independence.
Choice "a" is incorrect. Personal tax services provided to employees do not impair the auditor's independence; however, personal tax services provided to corporate officers or their families would impair independence.
Choice "b" is incorrect. Independence is not impaired by the performance of an audit of Perigee's internal control; in fact, such services are required by PCAOB Auditing Standard No. 5 (covered in a later class).
Choice "c" is incorrect. The prohibition against auditing companies whose corporate officers worked for the auditing firm only applies if those officers worked on the audit during the preceding year.