The correct answer is: a) Siang (Dihang).
The Siang (Dihang) is the largest tributary of the Brahmaputra River. It originates in the Himalayas in Tibet and flows through the Indian states of Arunachal Pradesh and Assam. The Siang is a major source of water for irrigation and hydroelectric power in the region.
The Subansiri, Kameng, and Lohit are also major tributaries of the Brahmaputra, but they do not originate in Tibet. The Subansiri originates in the Himalayas in Arunachal Pradesh, the Kameng originates in the Himalayas in Arunachal Pradesh and Bhutan, and the Lohit originates in the Himalayas in Tibet.
The Brahmaputra is the longest river in India and the ninth longest river in the world. It flows through the Indian states of Arunachal Pradesh, Assam, Nagaland, Manipur, Mizoram, Tripura, and Meghalaya, as well as the Bangladesh. The Brahmaputra is a major source of water for irrigation and hydroelectric power in the region.