Final answer:
Option 4: Prudence is not considered a prima facie duty by W.D. Ross. His prima facie duties were fidelity, reparation, gratitude, to promote the good, and non-maleficence.
Step-by-step explanation:
The option that is not a prima facie duty according to W.D. Ross is Option 4: Prudence. Ross identified several prima facie duties that are important moral commitments. These are (1) fidelity, (2) reparation, (3) gratitude, (4) to promote a maximum of aggregate good, and (5) non-maleficence. Prudence is not listed as one of his prima facie duties.
According to Ross, prima facie duties are based on moral principles that are apparent upon first sight and are self-evident through experience and maturity. In a situation where there is a conflict between duties, Ross believed in using judgement and a quasi-consequentialist approach to determine which duty should prevail, aiming for the "greatest balance of prima facie rightness over prima facie wrongness".