UPSC Civil Services 2016 Prelims General Studies Paper I

The Brahmaputra enters India in the state of Arunachal Pradesh from its original source Tibet, and is joined by the Dibang River and the Lohit River at the head of the Assam Valley. It is joined in Sonitpur by the Kameng River (or Jia Bhoreli).
Brahmaputra's main left bank tributaries, viz., Dibang or Sikang and Lohit. The important right bank tributaries are the Subansiri, Kameng, Manas and Sankosh. Therefore, all 3 correct.