The correct option is 1 and 3 only.
Explanation
The Brahmaputra river system traverses Tibet, India, and Bangladesh. In the Assam valley, the river generally flows from east to west. Consequently, tributaries joining from the north are Right Bank tributaries, while those joining from the south are Left Bank tributaries.
- Statement 1 is Correct: The Dibang and Lohit are major tributaries of the Brahmaputra. They join the Siang river (the name of the Brahmaputra in Arunachal Pradesh) from the east/southeast to form the main Brahmaputra river in the Assam plains. Geographically, they are considered left bank tributaries.
- Statement 2 is Incorrect: The Burhi Dihing originates in the Patkai Hills (Arunachal Pradesh) and flows through the Tinsukia and Dibrugarh districts of Assam. It joins the Brahmaputra from the south; therefore, it is a left bank tributary, not a right bank tributary.
- Statement 3 is Correct: The Dhansari (South) originates from the Laisang peak in Nagaland. It flows northwards through Dimapur and Golaghat to join the Brahmaputra on its south bank. Thus, it is a left bank tributary.
Key Takeaway:
Right Bank Tributaries: Subansiri, Kameng, Manas, Sankosh, Teesta.
Left Bank Tributaries: Burhi Dihing, Dhansari (South), Dibang, Lohit, Kopili.