Which of the following is not south bank tributary of the River Brahmaputra?

The river starts in Bhutan and travels through the Manas reserve forest before entering the Assamese plains close to Mathanguri.
This river splits into two branches at Mathanguri; the eastern branch is known as Beki and the western branch is Manas.
Near Jogighopa, the Manas River and the Brahmaputra River converge.