The correct option is "1 only" because, in the revenue administration of the Delhi Sultanate, the term ‘Amil’ was used to denote revenue officials responsible for tax collection, reflecting the administrative structure in place to manage agrarian resources. The Iqta system, while utilized by the Sultans of Delhi, was actually derived from earlier Islamic practices and evolved significantly under their rule, indicating it was not merely an indigenous institution. Lastly, the office of ‘Mir Bakshi’, responsible for military administration and pay, was established during the time of the Tughlaq dynasty and not specifically under the Khalji Sultans. Thus, only the first statement accurately describes a key feature of the Delhi Sultanate’s administrative framework.