During the reign of IItutmish, special slaves were purchased for military service known as ...............

Bandagan

The correct answer is Option 2- Bandagan

Special slaves purchased for military service during the reign of Iltutmish were known as Bandagan.

Bandagan were carefully trained and equipped, and they formed the core of the Sultan's army. They were also given important positions in the government, and many of them rose to become high-ranking officials.

Here's a breakdown of the other terms and why they aren't the answer:

Samanta: Samantas were hereditary landholders or chieftains who owed military service to the king in exchange for land grants. They weren't slaves but held a more independent position.
Iqtadar: Iqtadars were officials who received land grants (iqtas) from the Sultan. They were responsible for collecting taxes from the land and sometimes maintaining a small military force.  While some Iqtadars might have been former slaves, the term itself doesn't refer specifically to military slaves.
Muqtis: Similar to Iqtadars,  Muqtis were revenue collectors who received a share of the taxes collected from a particular area.  The term doesn't specifically refer to military slaves.