The correct answer is option 3, Gram Cooperative Society. A Panchayati Raj Institution is a system of local self-government in rural areas of India. It consists of three tiers: Gram Panchayat at the village level, Panchayat Samiti at the block level, and Zilla Parishad at the district level.

Option 1, Gram Sabha, is a primary unit of the Panchayati Raj System where all adult members of the village participate in decision-making processes. Option 2, Gram Panchayat, is the elected body at the village level responsible for the administration and development of the area.

Option 4, Nyaya Panchayat, is a small local court at the village level that resolves disputes using traditional customs and laws. However, option 3, Gram Cooperative Society, is not a Panchayati Raj Institution. Cooperative societies are voluntary associations formed to promote economic and social interests of members and are not part of the Panchayati Raj System.