The correct answer is option 1: Zilla Panchayat —> Block Panchayat —> Gram Panchayat —> Gram Sabha.

In the structure of Panchayati Raj, the Zilla Panchayat is the highest level of the system and is responsible for governance at the district level. Below the Zilla Panchayat, we have the Block Panchayat, which is responsible for governance at the block or taluka level. Further down the hierarchy, we have the Gram Panchayat, which is responsible for governance at the village level. The Gram Sabha is the basic unit of the Panchayati Raj system and consists of all the adult members in a village. It is the ultimate decision-making body at the village level.

Option 2, 3, and 4 are incorrect as they include entities like Khap Panchayat and Nagar Panchayat, which are not part of the traditional Panchayati Raj structure.