Choice "C" is correct. Preparing future financial statements constitutes a compilation of prospective financial statements, which is considered to be an attestation service.
Choices "a" and "d" are incorrect. Attestation engagements specifically exclude advocacy services and consulting services.
Choice "b" is incorrect. Attest engagements include those in which a practitioner is engaged to issue or does issue an examination, a review, or an agreed-upon procedures report on subject matter, or on an assertion about the subject matter, that is the responsibility of another party, as well as engagements related to prospective financial statements. Performing the role of in-house controller part-time does not fit into any of these categories.