The correct answer is: a) District.
A district is an administrative unit in India, below the state level. It is headed by a district magistrate, who is appointed by the state government. The district magistrate is responsible for the maintenance of law and order, revenue collection, and development work in the district.
A block is an administrative unit in India, below the district level. It is headed by a block development officer, who is appointed by the state government. The block development officer is responsible for the implementation of government schemes and programs in the block.
A panchayat is a local self-government body in India. It is headed by a sarpanch, who is elected by the people of the panchayat. The panchayat is responsible for the development work in the village.
A village is the smallest administrative unit in India. It is headed by a gram panchayat, which is elected by the people of the village. The gram panchayat is responsible for the day-to-day administration of the village.
The primary administrative unit in Sikkim is the district. There are four districts in Sikkim: East Sikkim, North Sikkim, South Sikkim, and West Sikkim. Each district is further divided into blocks. The blocks are further divided into villages.