Final answer:
In California, fee splitting, fee sharing, and referral fees are not permitted for mere recommendations.
Step-by-step explanation:
In California, all of the options mentioned - fee splitting rules, fee sharing rules, and referral fees - are not permitted for mere recommendations.
Fee splitting refers to the practice of dividing fees between two or more attorneys who are not in the same firm, while fee sharing refers to the sharing of legal fees between attorneys in different firms. Referral fees involve paying a fee to an attorney or non-attorney for recommending or referring a client. These practices are all restricted by the California Rules of Professional Conduct.
Therefore, the correct answer is None of the above.