Concept:The Farewell Sermon of Prophet Muhammad (SAW) discussed key social and economic reforms. Restricted polygamy was not among them.Explanation:The sermon clearly abolished all forms of usury or interest (riba).It commanded kindness and fair treatment toward slaves.It emphasised Islamic brotherhood, equality, and the unity of all Muslims.However, it did not impose any restriction on polygamy in this sermon.Therefore, restricted polygamy is not an issue mentioned in the Farewell Sermon.Answer:D. Restricted polygamy