Question: On which river is this city that has N'Dolo Airport situated?

full_context: Document 1: Ubangi River: The Ubangi River ( or ), also spelled Oubangui, is the largest right-bank tributary of the Congo River in the region of Central Africa. It begins at the confluence of the Mbomou and Uele Rivers and flows west, forming the border between Central African Republic (CAF) and Democratic Republic of the Congo. Subsequently, the Ubangi bends to the southwest and passes through Bangui, the capital of CAF, after which it flows southforming the border between Democratic Republic of the Congo and Republic of Congo. The Ubangi finally joins the Congo River at Liranga.
Document 2: History of the Inga dams: This is a history of the Inga dams, chronicling the various studies, plans, and projects that have aimed to harness the energy of the Congo River at the site of the Inga Falls, located north of Matadi in the Democratic Republic of the Congo (DRC). The immense potential of the Inga Falls was recognized in the early 1900s, though the first major hydroelectric project, initiated by the Belgians, did not come until the late 1950s. Two dams were built at the site during the rule of President Mobutu Sese Seko: Inga I was commissioned in 1972 and Inga II in 1982. Since then proposals have been put forth for an Inga III as well as a Grand Inga, which if built, would be the largest hydroelectric facility in the world.
Document 3: Air Kasaï: Air Kasaï is an airline with its head office on the property of N'Dolo Airport in Barumbu, Kinshasa, Democratic Republic of the Congo. It operates charter services within Africa. Its main base is N'Dolo Airport, Kinshasa.
Document 4: Filair: Filair is an airline based in the Democratic Republic of the Congo. Its operates from N'Dolo Airport, in Kinshasa. The airline is on the list of air carriers banned in the European Union, as are all airlines regulated by the authorities in the DRC.
Document 5: Air Tropiques: Air Tropiques is an airline based in Kinshasa, Democratic Republic of the Congo. It operates domestic, regional and charter flights. Its main base is N'Dolo Airport, Kinshasa.
Document 6: Dolo Airport: Dolo Airport is an airport serving Dolo in Ethiopia.
Document 7: Kasai River: The Kasai River (called Cassai in Angola) is a tributary of the Congo River, located in central Africa. The river begins in Angola and then serves as the border between Angola and the Democratic Republic of the Congo (DRC), until it flows into the DRC. The Kasai joins the Congo at Kwamouth northeast of Kinshasa. The Kasai's tributaries include the Fimi, Kwango, and Sankuru rivers. The short stretch of the Kasai from the inflow of the Fimi to the Congo is known as the Kwah River. The Kasai basin consists mainly of equatorial rainforest areas, which provide an agricultural land in a region noted for its infertile, sandy soil. It is a tributary of Congo river and diamonds are found in this river. Around 60% of diamonds in Belgium go from Kasai river for cutting and shaping.
Document 8: Kinshasa: Kinshasa ( ; ] ; formerly Léopoldville (French: "Léopoldville" or Dutch    )) is the capital and the largest city of the Democratic Republic of the Congo. It is situated on the Congo River.
Document 9: Kasai Allstars: Kasai Allstars are a 25-piece musical collective based in Kinshasa, Democratic Republic of the Congo. The musicians originally come from five bands, all from the Kasai region, but originating from five different ethnic groups: the Songye, Lulua, Tetela, Luba, and Luntu. Some of these groups have endured conflicting relationships over the centuries, they each have their own culture, their own language and their own musical traditions, which were always thought to be incompatible until these musicians decided to pool their resources and form a "superband", at the instigation of Belgian producer Vincent Kenis
Document 10: Democratic Republic of the Congo: The Democratic Republic of the Congo ( ; ] ; French: "République démocratique du Congo" ), also known as Zaire, DR Congo, East Congo, DRC, DROC, Congo-Kinshasa or simply the Congo, is a country located in Central Africa. The DRC borders the Central African Republic and South Sudan to the north; Uganda, Rwanda, Burundi and Tanzania to the east; Zambia and Angola to the south; the Republic of the Congo to the west and the Atlantic Ocean to the southwest. It is the second-largest country in Africa (largest in Sub-Saharan Africa) by area and eleventh largest in the world. With a population of over 80 million, the Democratic Republic of the Congo is the most populated officially Francophone country, the fourth most-populated nation in Africa and the seventeenth most populated country in the world.
Document 11: Malift Air: Malift Air was an airline based in Kinshasa, Democratic Republic of the Congo. It operated domestic passenger and cargo services from 1995 until 2009. Its main base was N'Dolo Airport, Kinshasa.
Document 12: Free Airlines: Free Airlines is an air operator out of N'Dolo Airport, Kinshasa, Democratic Republic of Congo.
Document 13: 1996 Air Africa crash: The 1996 Air Africa crash occurred on 8 January when an overloaded Air Africa Antonov An-32B aircraft, wet leased from Moscow Airways and bound for Kahemba Airport, overshot the runway at N'Dolo Airport in Kinshasa, Democratic Republic of the Congo after failing to take off and ploughed into Kinshasa's Simbazikita street market. Though four of the aircraft's six crew survived, 225 fatalities and around 253 serious injuries occurred on the ground. This is the largest number of non-passenger ground fatalities caused by the accidental crash of an aircraft.
Document 14: Lubaland: Lubaland refers to the savanah grassland south of the Congo River where the Luba people live; now the southeastern portion of the Democratic Republic of the Congo. Around 1500 CE Lubas united to form a kingdom which was ultimately taken over in 1885 by Leopold II, King of Belgium, who made it part of his Congo Free State. Lubaland stretches from the Lwembe river to about 50 kilometers east of the Congo River, between 6°30′ and 10°00′ S in north-central Shaba. The area is a savanah except Upemba Depression.
Document 15: N'Dolo Airport: N'Dolo Airport (IATA: NLO, ICAO: FZAB) , also known as Ndolo Airport, is a secondary airport in the city of Kinshasa, Democratic Republic of the Congo, located in the commune of Barumbu near the city center.
ground_truth: Congo River