The southern part of Bihar, characterized by undulating terrain and forested areas, is part of the:

Thar Desert
Western Ghats
Chota Nagpur Plateau
Eastern Coastal Plains

The correct answer is: c) Chota Nagpur Plateau.

The Chota Nagpur Plateau is a large plateau in eastern India. It is located in the states of Jharkhand, Chhattisgarh, Odisha, and Bihar. The plateau is characterized by its undulating terrain and forested areas. It is a major source of coal and iron ore.

The Thar Desert is a desert in northwestern India and eastern Pakistan. It is the largest hot desert in Asia. The desert is characterized by its sandy dunes, scrubby vegetation, and extreme temperatures.

The Western Ghats are a mountain range in western India. They are the second-highest mountain range in India, after the Himalayas. The Western Ghats are a popular tourist destination, known for their scenic beauty and biodiversity.

The Eastern Coastal Plains are a plain in eastern India. They are located along the Bay of Bengal. The plains are characterized by their fertile soil and tropical climate. They are a major agricultural region.