बिहार में गंगा की उत्तरी सहायक नदियों में सबसे लम्बी नदी कोसी है, उसकी लम्बाई बिहार में है- - Kosi is the longest river in Bihar among the northern tributaries of the Ganges, its length in Bihar is- - Bihar Me Ganga Ki Uttari Sahayak Nadiyon Me Sabse Lambi Nadi Kosi Hai , Uski Lambai Bihar Me Hai - Bihar Gk in hindi, Drainage System 120 Kilometer question answers in hindi pdf 125 Kilometer questions in hindi, Know About 115 Kilometer Bihar Gk online test Bihar Gk notes in hindi quiz book 130 Kilometer