The correct answer is: b) Alluvial Plains.
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 Bangladesh to the south-west and west. The Brahmaputra River flows through the state, and the Barak River flows through the south-eastern part of the state.
The predominant landform in Assam is alluvial plains. These plains are formed by the deposition of sediments from the Brahmaputra River and its tributaries. The plains are fertile and are used for agriculture. The climate in Assam is tropical monsoonal. The summers are hot and humid, and the winters are cool and dry.
The other options are:
- Mountainous: This option is incorrect because Assam is not a mountainous state.
- Desert: This option is incorrect because Assam is not a desert.
- Coastal Plains: This option is incorrect because Assam does not have coastal plains.