With respect to medieval history zimmi refers to the category of ........

Ancient and Medival History Mughal Period

With respect to medieval history, zimmi refers to the category of :

people who followed revealed scriptures, such as the Jews and Christians, and lived under Muslim rulers.

people who often revolted against Muslim rulership and rejected their authority.

slaves who enjoyed certain privileges in comparison to other slaves.

people belonging to the radical sects of Islam like Qalandars and Madaris

Muslim rulers were theoretically to be guided by the ulama, who were expected to ensure that they ruled according to the shari‘a. However, the situation was complicated in the subcontinent, where there were populations that did not subscribe to Islam.
It is in this context that the category of the zimmi (derived from the Arabic word zimma, protection), developed for peoples who followed revealed scriptures (like Bible, Quran, Vedas, etc), such as the Jews and Christians, and lived under Muslim rulership. They paid a tax called jizya and gained the right to be protected by Muslims. In India this status was extended to Hindus as well.
Hence, option (a) is the correct answer.