The correct answer is: a) Himalayas, Plains, Hills.
Assam is a state in north-eastern India. It is bordered by Bhutan to the north, Arunachal Pradesh to the north-east, Nagaland to the east, Manipur to the south-east, Mizoram to the south, Tripura to the south-west, Meghalaya to the west, and West Bengal to the southwest and west. The state is divided into three main regions: the Brahmaputra Valley, the Barak Valley, and the Hill Areas.
The Brahmaputra Valley is the largest region in Assam. It is located in the north-central part of the state and is drained by the Brahmaputra River. The valley is a fertile plain with a rich agricultural history. The Barak Valley is located in the south-eastern part of the state and is drained by the Barak River. The valley is a hilly region with a tropical climate. The Hill Areas are located in the north-eastern and eastern parts of the state. They are a mountainous region with a temperate climate.
The Himalayas are a mountain range that runs along the northern border of Assam. The Himalayas are the highest mountain range in the world and are home to some of the world’s most famous peaks, including Mount Everest. The Plains are a vast lowland area that covers most of the state of Assam. The Plains are a fertile region with a rich agricultural history. The Hills are a hilly region that covers the eastern and northeastern parts of the state. The Hills are a mountainous region with a temperate climate.