sentences:  The river and its tributaries form the backbone of Congolese economics and transportation.Major tributaries include the Kasai, Sangha, Ubangi, Ruzizi, Aruwimi, and Lulonga.The sources of the Congo are in the Albertine Rift Mountains that flank the western branch of the East African Rift, as well as Lake Tanganyika and Lake Mweru.