Select the Correct statement regarding Contingent fees

A. The PCAOB rules provide an exception to a prohibition of contingent fees when set by the courts. B. The PCAOB and SEC provide an exception for contingent fees wher it involves tax services for a claim of refund where the state has a prescribed review process of the claim. C. The AICPA permits a contingent fee when representing a client who is seeking a private letter ruling from the IRS. D. The AICPA permits contingent fees for preparation of an original return for an audit client