Which of the Following Fee Arrangements Is Not a Violation

Which of the following fee arrangements is not a violation of the AICPA's Code of Professional Conduct?

A) basing fees as an expert witness on the amount awarded to the plaintiff, even though the CPA performs a compilation for client use
B) basing consulting fees on a percentage of a bond issue, even though the CPA performs a review of the client's financial statements
C) basing fees for a tax service on the amount of the refund that the client will receive
D) basing consulting fees on a percentage of a bond issue, even though the CPA performs an audit of the client's financial statements