The correct answer is: c) 900 km.
The Brahmaputra is the longest river in India and the third longest river in Asia. It originates in the Himalayas in Tibet and flows through India and Bangladesh. The Brahmaputra is a major source of water for irrigation and drinking water in Assam. It is also a major transportation route.
The Brahmaputra enters Assam from Tibet in the north and flows south through the state. It then turns east and flows into Bangladesh. The Brahmaputra is about 900 km long within Assam. It is a major river in Assam and is an important part of the state’s economy and culture.
The other options are incorrect because they are not the approximate length of the Brahmaputra within Assam. Option a) is 450 km, which is too short. Option b) is 650 km, which is too long. Option d) is 1200 km, which is too long.