Choice "D" is correct. Failure to return records to a client after the client makes a demand is considered to be an act discreditable to the profession, and as such violates the profession’s ethical standards.
Choice "b" is incorrect. There is no prohibition against using a records-retention agency to store confidential client records.
Choice "c" is incorrect. Arranging with a financial institution to collect notes issued by a client in payment of fees due does not violate the profession’s ethical standards.
Choice "a" is incorrect. A compilation of financial statements does not require the auditor to be independent (although the lack of independence should be disclosed).