You will be given a definition of a task first, then some input of the task.
In this task, you are given a context, a subject, a relation, and many options. Based on the context, from the options select the object entity that has the given relation with the subject. Answer with text (not indexes).

Context: The Democratic Republic of the Congo , also known as DR Congo, DRC, DROC, East Congo, Congo-Kinshasa, or simply the Congo is a country located in Central Africa. From 1971 to 1997 it was named, and is sometimes still called Zaire, and from 1908 to 1960 it was called the Belgian Congo. 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 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 eighteenth most populated country in the world., A prefecture (from the Latin "Praefectura") is an administrative jurisdiction or subdivision in any of various countries and within some international church structures, and in antiquity a Roman district governed by an appointed prefect., Bangui, or Bangî in Sango, formerly written Bangi in English, is the capital and largest city of the Central African Republic. it had an estimated population of 734,350. It was established as a French outpost in 1889 and named after its location on the northern bank of the Ubangi River; the Ubangi itself was named from the Bobangi word for the "rapids" located beside the settlement, which marked the end of navigable water north from Brazzaville. The majority of the population of the Central African Republic lives in the western parts of the country, in Bangui and the surrounding area., Central Africa is a core region of the African continent which includes Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, and Rwanda. Middle Africa (as used by the United Nations when categorising geographic subregions) is an analogous term that includes Angola, Cameroon, the Central African Republic, Chad, the Republic of the Congo, the Democratic Republic of the Congo, Equatorial Guinea, Gabon, and São Tomé and Príncipe. All of the states in the UN subregion of Middle Africa, plus those otherwise commonly reckoned in Central Africa (11 states in total), constitute the Economic Community of Central African States (ECCAS). Since its independence in 2011, South Sudan has also been commonly included in the region., The Republic of the Congo, also known as the Congo Republic, West Congo, Congo-Brazzaville or simply Congo, is a country located in Central Africa. It is bordered by five countries: Gabon and the Atlantic Ocean to the west; Cameroon to the northwest; the Central African Republic to the northeast; the Democratic Republic of the Congo to the east and south; and the Angolan exclave of Cabinda to the southwest., Sudan ("as-Sdn", ), also known as North Sudan and officially the Republic of the Sudan ("Jumhriyyat as-Sdn"), is a country in Northern Africa. It is bordered by Egypt to the north, the Red Sea, Eritrea, and Ethiopia to the east, South Sudan to the south, the Central African Republic to the southwest, Chad to the west and Libya to the northwest. It is the third largest country in Africa. The River Nile divides the country into eastern and western halves. Before the Sudanese Civil War, South Sudan was part of Sudan but broke away in 2011. Its predominant religion is Islam., Cameroon, officially the Republic of Cameroon, is a country in Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the Bight of Bonny, part of the Gulf of Guinea and the Atlantic Ocean., Bossangoa is the capital of Ouham, one of the 14 prefectures of the Central African Republic. The town has a population of 36,478 (2003 census). It is located 303 km (189 mi) north of the country's capital, Bangui. The Ouham River passes through Bossangoa and on through a number of waterfalls east of the city before turning north to join the Chari River in Chad., The Central African Republic (CAR; Sango: "Ködörösêse tî Bêafrîka";   , or "" ) is a landlocked country in Central Africa. It is bordered by Chad to the north, Sudan to the northeast, South Sudan to the east, the Democratic Republic of the Congo and the Republic of the Congo to the southwest and Cameroon to the west. The CAR covers a land area of about and had an estimated population of around 4.7 million ., The Ouham River is a river in Central Africa, and one of the main headwaters of the Chari River. The Ouham originates in the Central African Republic between the prefecture Nana-Mambéré and the prefecture Ouham-Pendé, crossing into Chad where it joins the Chari about 25 km north Sarh. Tributaries are Baba, Fafa, Nana Bakassa, Nana Barya., Chad ('), officially the Republic of Chad ('), is a landlocked country in Central Africa. It is bordered by Libya to the north, Sudan to the east, the Central African Republic to the south, Cameroon and Nigeria to the southwest and Niger to the west. It is the fifth largest country in Africa in terms of area., Ouham is one of the 14 prefectures of the Central African Republic . Its capital is Bossangoa ., A landlocked state or landlocked country is a sovereign state entirely enclosed by land, or whose only coastlines lie on closed seas. There are currently 48 such countries, including four partially recognised states. Only two, Bolivia and Paraguay in South America, lie outside Afro-Eurasia (the Old World)., Subject: ouham, Relation: named_after, Options: (A) 11 (B) africa (C) angola (D) atlantic ocean (E) capital (F) central (G) church (H) city (I) democratic republic of the congo (J) egypt (K) english (L) libya (M) lie (N) nation (O) nigeria (P) north (Q) northeast (R) ouham river (S) republic of the congo (T) sea (U) south (V) west
Output:
ouham river