The correct answer is (a) Brahmaputra.
The Brahmaputra is the largest river in Assam, and it is also the largest river in India by volume. The Brahmaputra basin is home to a wide variety of fish species, including carp, catfish, and mahseer. Freshwater fishing is a major source of income for many people in Assam.
The Barak is the second largest river in Assam. It is a tributary of the Brahmaputra, and it flows through the Barak Valley in the southern part of the state. The Barak basin is also home to a variety of fish species, but it is not as important for freshwater fishing as the Brahmaputra basin.
The Ganga is the longest river in India, and it is the most important river in the country for both religious and economic reasons. The Ganga does not flow through Assam, but it does have a significant impact on the state’s climate and water resources.
The Mahanadi is a river in central India. It is the fifth longest river in India, and it is the largest river in the state of Odisha. The Mahanadi does not flow through Assam, and it does not have a significant impact on the state’s freshwater fishing industry.