Concept:Diwan-i-Arz was the military department of the Delhi Sultanate, established by Sultan Balban to manage the royal army.
Explanation:The term "Diwan-i-Arz" refers to the Department of Military Affairs in the Delhi Sultanate.
It was created by Balban (Ghiyas ud din Balban), the ninth ruler of the Mamluk dynasty.
The head of this department, called Ariz-i-Mamalik, was responsible for the regulation and maintenance of the royal army.
In contrast, the chief revenue department was Diwan-i-Wizarat, the executive wing was the Sultan himself and his ministers, and the maritime department was under Amir-i-bahr.
Thus, among the given options, only option D correctly describes the diwan-i-arz.
Answer:D. the military department in the Sultanate