A traditional method of grazing livestock in the hills of Tamil Nadu is known as:

Penning
Paddock system
Nomadism
Zero grazing

The correct answer is: Paddock system.

Paddock system is a traditional method of grazing livestock in the hills of Tamil Nadu. It is a rotational grazing system in which livestock are moved from one paddock to another to allow the pastures to recover. This system helps to prevent overgrazing and soil erosion.

Penning is a method of grazing livestock in which they are confined to a small area. This system is often used in areas where there is limited grazing land. Penning can help to control the spread of disease and parasites.

Nomadism is a lifestyle in which people move from place to place in search of food and water. Nomadic herders often move their livestock with them. This system is often used in areas where there is little rainfall and where the land is not suitable for agriculture.

Zero grazing is a method of grazing livestock in which they are fed hay or other feedstuffs that have been grown on a different piece of land. This system is often used in areas where there is little grazing land or where the land is not suitable for grazing.

Paddock system is the most common method of grazing livestock in the hills of Tamil Nadu. It is a sustainable method of grazing that helps to protect the environment.