The term 'chakla' has been used in Medieval Indian History sources. It was-

The correct answer is C. In Mughal administration, a chakla was a territorial unit larger than a pargana, made up of several parganas, and it sat in the administrative hierarchy between the subah and the pargana. It was not the same as the sarkar, which was the more common intermediate unit in the Ain-i-Akbari scheme. Chaklas were often placed under a faujdar for law and order, and in some regions they served as a revenue-collection and military circle.

• A is wrong. A pargana was the basic revenue and administrative unit. A chakla was an aggregate of parganas, so the two cannot be identical.
• B is wrong. Sarkar and chakla were related but distinct. Sources use the terms with some overlap, so the distinction needs care, but the question asks for the unit that is not identical to sarkar.
• D is wrong because C correctly describes the unit.

The core concept is the layered Mughal territorial structure of subah, sarkar, chakla, and pargana, which Irfan Habib's The Agrarian System of Mughal India explains. For Mains, this structure is useful for questions on centralised administration and the link between revenue assessment and local power.

Trap: Candidates treat chakla as a synonym of sarkar, or as a pargana, because the terms overlap in the sources.