Answer
D. It protected the sultan’s power by providing him with a group of extremely loyal officials and soldiers.
Step-by-step explanation
The palace schools where a portion of the master's youngsters were taught and brought were available up in the Carolingian Empire, in the Habsburgs and in Britain since the Charlemagne. Likewise the mounted force and infantry units which Ottomans called "kapıkulu" can be found in the Austria with the name "Leibgardist", and in Russia with the name "Strelitsiy" (gunsmith). Truth be told, this military called strelitsiy was completely expelled by Peter the Great amid the modernization time frame, much the same as Mahmud II evacuated the janissaries.