The correct answer is: D. Mahananda plain
The Mahananda plain is a plain in the Indian state of Bihar. It is located in the south-central part of the state, and is bounded by the Ganges River to the north, the Son River to the east, the Jharkhand state to the south, and the Central South Bihar plain to the west. The Mahananda plain is a fertile region, and is home to a number of important cities, including Patna, Gaya, and Bhagalpur.
The Mahananda plain is a part of the Indo-Gangetic Plain, which is the largest plain in India. The Indo-Gangetic Plain is a vast alluvial plain that is formed by the deposition of sediments from the Ganges and Brahmaputra rivers. The plain is home to a large number of people, and is one of the most important agricultural regions in India.
The Mahananda plain is a relatively flat plain, with an average elevation of about 100 meters above sea level. The plain is drained by a number of rivers, including the Mahananda River, the Son River, and the Ganges River. The climate of the Mahananda plain is tropical, with hot, humid summers and cool, dry winters.
The Mahananda plain is a fertile region, and is home to a number of important crops, including rice, wheat, sugarcane, and jute. The plain is also home to a number of important industries, including agriculture, manufacturing, and mining.
The Mahananda plain is a beautiful and historic region, and is home to a number of important cultural and historical sites. The plain is also home to a number of important wildlife sanctuaries, including the Sanjay Gandhi National Park and the Valmiki Tiger Reserve.