The correct answer is A. The North Bihar plain.
The North Bihar plain is a physiographic division of Bihar, India. It is a vast alluvial plain that is drained by the Ganges River and its tributaries. The plain is characterized by its fertile soil and its flat topography. It is a major agricultural region and is also home to a number of important cities, including Patna, the capital of Bihar.
The South Bihar plain is a physiographic division of Bihar, India. It is a smaller plain than the North Bihar plain and is located to the south of the Ganges River. The plain is characterized by its hilly terrain and its less fertile soil. It is a less developed region than the North Bihar plain and is home to a smaller population.
The Shiwalik range is a mountain range that is located in the northern part of India. The range is a part of the Himalayas and is a popular tourist destination. The Shiwalik range is not a physiographic division of Bihar.
The Southern hilly range is a mountain range that is located in the southern part of India. The range is a part of the Western Ghats and is a popular tourist destination. The Southern hilly range is not a physiographic division of Bihar.