The correct answer is option 2: Alauddin Khalji.

During the Sultanate period, Alauddin Khalji, who ruled from 1296 to 1316, created the largest standing army directly paid by the state. He introduced various reforms to strengthen and organize the army. One of his significant reforms was the introduction of the "dagh" system, which involved branding horses owned by soldiers to prevent theft and ensure proper control over the army. Alauddin Khalji also implemented a system called the "chehra", which involved regular inspections of soldiers and their loyalty. These reforms helped Alauddin Khalji establish a powerful and disciplined military force that played a crucial role in expanding the Delhi Sultanate`s territories and maintaining its control over the regions.