The correct option is C Tirthas
In his Saptanga Theory, Kautilya enumerates seven prakritis or essential organs of the state. They are Swamin, Amatya, Janapad, Durga, Kosha, Danda and Mitra.
Tirthas are not the part of Saptanga, as proposed by Kautilya in his Arthashastra.