Information:  - An ocean (the sea of classical antiquity) is a body of saline water that composes much of a planet's hydrosphere. On Earth, an ocean is one of the major conventional divisions of the World Ocean, which covers almost 71% of its surface. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans. The word "sea" is often used interchangeably with "ocean" in American English but, strictly speaking, a sea is a body of saline water (generally a division of the world ocean) partly or fully enclosed by land.  - A tributary or affluent is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainage basin of its surface water and groundwater, leading the water out into an ocean.  - Malawi (or ; or [maláwi]), officially the Republic of Malawi, is a landlocked country in southeast Africa that was formerly known as Nyasaland. It is bordered by Zambia to the northwest, Tanzania to the northeast, and Mozambique on the east, south and west. The country is separated from Tanzania and Mozambique by Lake Malawi. Malawi is over with an estimated population of 16,777,547 (July 2013 est.). Its capital is Lilongwe, which is also Malawi's largest city; the second largest is Blantyre, the third is Mzuzu and the fourth largest is its old capital Zomba. The name Malawi comes from the Maravi, an old name of the Nyanja people that inhabit the area. The country is also nicknamed "The Warm Heart of Africa".  - Tanzania , officially the United Republic of Tanzania, is a country in Eastern Africa within the African Great Lakes region. Parts of the country are in Southern Africa. It is bordered by Kenya and Uganda to the north; Rwanda, Burundi, and the Democratic Republic of the Congo to the west; Zambia, Malawi, and Mozambique to the south; and by the Indian Ocean to the east. Mount Kilimanjaro, Africa's highest mountain, is in northeastern Tanzania.  - The Dwangwa River in Malawi is a tributary river for Lake Nyasa . It flows for approximately 100 miles ( 160 km ) . The river 's source is in the Kasungu National Park , in Malawi 's central plateau . It flows north - easterly from this plateau through an ancient valley . The river 's mouth flows out of a more recently cut gorge , into the Lake . It also flows through the Bana Swamp The Dwangwa River is used both for irrigation and the generation of hydroelectric power . It is a fishing river , with prawns found in the river .  - Mozambique (or ), officially the Republic of Mozambique (or "") is a country in Southeast Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west, and Swaziland and South Africa to the southwest. It is separated from Madagascar by the Mozambique Channel to the east. The capital and largest city is Maputo (known as "Lourenço Marques" before independence).  - Lake Malawi, also known as Lake Nyasa in Tanzania and Lago Niassa in Mozambique, is an African Great Lake and the southernmost lake in the East African Rift system, located between Malawi, Mozambique and Tanzania. It is the ninth largest lake in the world and the third largest and second deepest lake in Africa. It is home to more species of fish than any other lake, including about 1000 species of cichlids. The Mozambique portion of the lake was officially declared a reserve by the Government of Mozambique on June 10, 2011,while in Malawi a portion of the lake is included in Lake Malawi National Park. Lake Malawi is a meromictic lake, meaning that its water layers do not mix. The permanent stratification of Lake Malawi's water and the oxic-anoxic boundary (relating to oxygen in the water) are maintained by moderately small chemical and thermal gradients.  - A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as stream, creek, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "burn" in Scotland and northeast England, and "beck" in northern England. Sometimes a river is defined as being larger than a creek, but not always: the language is vague.  - A sea is a large body of salt water that is surrounded in whole or in part by land. More broadly, "the sea" is the interconnected system of Earth's salty, oceanic watersconsidered as one global ocean or as several principal oceanic divisions. The sea moderates Earth's climate and has important roles in the water cycle, carbon cycle, and nitrogen cycle. Although the sea has been traveled and explored since prehistory, the modern scientific study of the seaoceanographydates broadly to the British "Challenger" expedition of the 1870s. The sea is conventionally divided into up to five large oceanic sectionsincluding the International Hydrographic Organization's four named oceans (the Atlantic, Pacific, Indian, and Arctic) and the Southern Ocean; smaller, second-order sections, such as the Mediterranean, are known as "seas".  - A drainage basin or catchment basin is an extent or an area of land where all surface water from rain, melting snow, or ice converges to a single point at a lower elevation, usually the exit of the basin, where the waters join another body of water, such as a river, lake, reservoir, estuary, wetland, sea, or ocean. Thus if a tributary stream joins a brook that in turn joins a small river which is a tributary of a larger river, there is a series of successively larger (and lower elevation) drainage basins. For instance, the Missouri and Ohio rivers are within their own drainage basins and also within the drainage basin of the Mississippi River.  - "Main Stem" is 1942 instrumental by Duke Ellington and His Famous Orchestra. Although recorded in 1942, the single would not be released until 1944 where it was Duke Ellington's last of four number one's on the Harlem Hit Parade. "Main Stem" also peaked at number twenty on the pop chart.    After reading the paragraphs above, choose the best answer for the entity that related to 'dwangwa river' with the relationship of 'mouth of the watercourse'.  Choices: - indian ocean  - lake malawi  - main  - mississippi river  - mozambique channel  - sea
A:
lake malawi