An audit of historical financial statements is a form of: Select one: a. assurance service in which the auditor issues a written report expressing an opinion about whether the financial statements are in material conformity with auditing standards. b. attestation service in which the auditor issues a written report expressing an opinion about whether the financial statements are in material conformity with auditing standards. attestation service in which the auditor issues a written report expressing an opinion about whether the financial statements are in material conformity with accounting standards. O d. none of the above