Concept:Baytul Mal is the Islamic public treasury, and its funds come from lawful sources such as Kharaj.Explanation:Baytul Mal is the state treasury in an Islamic economy.It receives income from several legitimate sources.Kharaj is an Islamic tax levied on agricultural land and its produce.Therefore, Kharaj is a valid and recognised source of funds for Baytul Mal.Amanah (trusts), Riba (interest), and Tatfif (fraudulent dealing) are not sources of income.Answer:B. Kharaj