Answer the following question: Information:  - Canada (French: ) is a country in the northern half of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering , making it the world's second-largest country by total area and the fourth-largest country by land area. Canada's border with the United States is the world's longest land border. The majority of the country has a cold or severely cold winter climate, but southerly areas are warm in summer. Canada is sparsely populated, the majority of its land territory being dominated by forest and tundra and the Rocky Mountains. About four-fifths of the country's population of 36 million people is urbanized and live near the southern border. Its capital is Ottawa, its largest city is Toronto; other major urban areas include Montreal, Vancouver, Calgary, Edmonton, Quebec City, Winnipeg and Hamilton.  - North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be considered a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.  - Edmonton is the capital city of the Canadian province of Alberta. Edmonton is on the North Saskatchewan River and is the centre of the Edmonton Capital Region, which is surrounded by Alberta's central region.  - The Long Range Mountains are a series of mountains along the west coast of the Canadian island of Newfoundland. They also form the northernmost section of the Appalachian chain on the eastern seaboard of North America. In 2003 it was announced that the International Appalachian Trail would be extended through the Long Range Mountains.  - Main River is a river in Newfoundland , Canada , a very popular canoeing destination . It is 57 km long , originates in the Long Range Mountains and enters the sea at White Bay . Main River was designated a Canadian Heritage River in February 2001 .  - Calgary is a city in the Canadian province of Alberta. It is situated at the confluence of the Bow River and the Elbow River in the south of the province, in an area of foothills and prairie, about east of the front ranges of the Canadian Rockies. In the 2011 census, the City of Calgary had a population of 1,096,833 and a metropolitan population of 1,214,839, making it the largest city in Alberta, and the third-largest municipality and fifth-largest census metropolitan area (CMA) in Canada.  - The International Appalachian Trail (IAT SIA) is a hiking trail which runs from the northern terminus of the Appalachian Trail at Mount Katahdin, Maine, through New Brunswick, to the Gaspé Peninsula of Quebec, after which it takes a ferry ride to Newfoundland, and then continues to the northern-easternmost point of the Appalachian Mountains at Belle Isle, Newfoundland and Labrador.  - Ottawa is the capital city of Canada. It stands on the south bank of the Ottawa River in the eastern portion of southern Ontario. Ottawa borders Gatineau, Quebec; the two form the core of the OttawaGatineau census metropolitan area (CMA) and the National Capital Region (NCR). The 2011 census reported a population of 883,391, making it the fourth-largest city in Canada; and 1,236,324 within the CMA, making it the fourth-largest CMA in Canada. The City of Ottawa reported that the city had an estimated population of 960,754 as of December 2015.    After reading the paragraphs above, we are interested in knowing the entity with which 'main river ' exhibits the relationship of 'mouth of the watercourse'. Find the answer from the choices below.  Choices: - arctic ocean  - atlantic ocean  - bow river  - isle  - maine  - north saskatchewan river  - ottawa river  - sea
Answer:
atlantic ocean