Answer:
d. converted to islam and trained as foot soldiers or administrators to serve the sultan.
Explanation:
The janissaries constituted infantry units with a high level of training. Among his many missions he emphasized the responsibility of the custody and safeguarding of the Ottoman sultan, as well as the dependencies of the imperial palace of Edirne and, later, of the new imperial palace Topkapi of Istanbul; they were considered the Praetorian Guard of the Sultan. The body was created by Bey Orhan I around 1330, and was abolished in 1826 by decree of Sultan Mahmud II.
Bey Orhan I, ruler of the incipient Ottoman Empire, founded the military corps of the Janissaries around 1330. It was originally formed by non-Muslim combatants, especially Christian prisoners of war. Orhan was perhaps influenced by the Mamluk sultans for the creation of this model military corps. The Janissaries became the first permanent Ottoman army, replacing forces that were mainly tribal warriors, whose loyalty and morals could not always be trusted. In addition, no free combatant (not enslaved) would consent to be an infantryman, considering the risky fate assigned to him.