The correct answer is: c) Brahmaputra.
The Gangetic River Dolphin is a freshwater dolphin found in the Ganges, Brahmaputra, and Indus river systems in South Asia. It is the most widely distributed of the world’s four river dolphin species. The Gangetic River Dolphin is a shy and elusive creature, and little is known about its population size or ecology. However, it is believed to be declining due to habitat loss, pollution, and overfishing.
The Manas River is a tributary of the Brahmaputra River in Assam, India. It is a major river in the state, and is home to a variety of wildlife, including the Gangetic River Dolphin. The Dhansiri River is another tributary of the Brahmaputra River, and is also home to the Gangetic River Dolphin. However, the Dhansiri River is a much smaller river than the Manas River, and is not as important a habitat for the dolphin. The Barak River is a major river in the state of Assam, and is not home to the Gangetic River Dolphin.
The Gangetic River Dolphin is a protected species in India, and is listed as Endangered on the IUCN Red List. However, the species is still facing a number of threats, and its population is declining. It is important to protect the Gangetic River Dolphin and its habitat, in order to ensure its survival.