The agro-climatic zone with the highest agricultural productivity in Tamil Nadu is:

Cauvery Delta Zone
Western Zone
North Eastern Zone
High Rainfall Zone

The correct answer is: Cauvery Delta Zone.

The Cauvery Delta Zone is the most fertile region in Tamil Nadu, and is home to the state’s most productive agricultural land. The region is well-irrigated by the Cauvery River, and receives an average annual rainfall of over 1,000 mm. This combination of factors makes the Cauvery Delta Zone ideal for growing a variety of crops, including rice, sugarcane, cotton, and vegetables.

The Western Zone is also a major agricultural region in Tamil Nadu, but it is not as fertile as the Cauvery Delta Zone. The Western Zone receives less rainfall than the Cauvery Delta Zone, and is more prone to drought. As a result, the Western Zone is not as well-suited for growing rice, but it is suitable for growing crops such as millet, sorghum, and pulses.

The North Eastern Zone is the least developed region in Tamil Nadu, and is not as well-suited for agriculture as the other two zones. The North Eastern Zone receives less rainfall than the other two zones, and is more prone to drought. As a result, the North Eastern Zone is not as well-suited for growing crops, and most of the land in the region is used for grazing.

The High Rainfall Zone is located in the Western Ghats, and receives an average annual rainfall of over 2,000 mm. The high rainfall makes the High Rainfall Zone ideal for growing crops such as tea, coffee, and cardamom. However, the high rainfall also makes the region prone to landslides and floods.