Turkish state structure has been complex, to say the least. Turks, starting with the Kok Turk Empire, administered their state by dividing it into two parts: East and West. East would be ruled by the more senior khagan. To prevent succession wars, which resulted in the weakening and destruction of so many Central Asian states of nomadic origin, Turks came up with a system whereby brothers would serve in age order. When the youngest of the brothers died, it would be the turn of the sons of the oldest brother. However, this system was never successful in totally preventing struggles for accession to the throne, given the abundance of princes who were just too impatient. At the end of the day, any member of the ruling clan had the right to claim the heavenly mandate (kut) to govern. Turks viewed the state as belonging to the ruling clan or tribe. Other than the main east / west division, there were territorial grants to nobles called ikta as payment for serving the state. Later, in the Ottoman Empire a similar timar system was introduced, which was also influenced by the Byzantine system. The correct answer is D.