Final answer:
Acceptance of any referral fees does not violate the Principle of Fairness if the nature and source of the referral fee is disclosed in writing to each referred client.
Step-by-step explanation:
The ethical aspect of the situation described in the question is best reflected in option D. Acceptance of any referral fees does not violate the Principle of Fairness found in the Code of Ethics and Professional Responsibility if the nature and source of the referral fee is disclosed in writing to each referred client.
Receiving referral fees is not inherently unethical, as long as there is transparency and disclosure. In this case, Bruce refers clients to Mark Mason without a formal arrangement, but Mr. Mason pays a referral fee. As long as Bruce discloses this arrangement to the referred clients in writing, it does not violate the Principle of Fairness.
It's worth noting that although the referral fee itself is not unethical, Bruce still has an obligation to research Mr. Mason's competence and ensure he is a competent bankruptcy attorney, as stated in option A. However, this obligation is separate from the ethical aspect of accepting referral fees.