Explanation:

More than one of the above 

• The Ganga flowing from west to east in this state is the main drainage channel with seven major rivers/basins namely :

                  Ghaghra, Gandak, Burhi-Gandak, Kamla Balan, Bagmati, Kosi and Mahananda on its North and

                  six namely Karmnasa, Sone, Punpun, Kiul-Harohar, Badua and Chandan on its south.

From the given options, all are the north flowing rivers of Bihar, so the answer will be more than one of the above.