Choice "A" is correct. General guidance provided by a Statement on Auditing Standards is the most authoritative of level of auditing guidance for audits of nonissuers. Auditors are required to comply with SASs, and should be prepared to justify any departures therefrom.
Choices "c" and "b" are incorrect. AICPA audit and accounting guides and SAS interpretations are interpretive publications that provide guidance regarding how SASs should be applied in specific situations. They are not as authoritative as SASs.
Choice "d" is incorrect. Journal of Accountancy articles have no authoritative status but may be helpful to the auditor.