Answer the following question: Information:  - The Saint Francis River is a tributary of the Mississippi River , about 426 miles ( 686 km ) long , in southeastern Missouri and northeastern Arkansas in the United States . The river drains a mostly rural area and forms part of the Missouri - Arkansas state line along the western side of the Missouri Bootheel .  - The Mississippi River is the chief river of the largest drainage system on the North American continent. Flowing entirely in the United States (although its drainage basin reaches into Canada), it rises in northern Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains all or parts of 31 U.S. states and 2 Canadian provinces between the Rocky and Appalachian Mountains. The Mississippi ranks as the fourth longest and fifteenth largest river in the world by discharge. The river either borders or passes through the states of Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana.  - The tallgrass prairie is an ecosystem native to central North America. Natural and anthropogenic fire, as well as grazing by large mammals (primarily bison), were historically agents of periodic disturbance, which regulates tree encroachment, recycles nutrients to the soil, and catalyzes some seed dispersal and germination processes. Prior to widespread use of the steel plow, which enabled conversion to agricultural land use, tallgrass prairies expanded throughout the American Midwest and smaller portions of southern central Canada, from the transitional ecotones out of eastern North American forests, west to a climatic threshold based on precipitation and soils, to the southern reaches of the Flint Hills in Oklahoma, to a transition into forest in Manitoba.   - Minnesota (locally ) is a state in the midwestern and northern regions of the United States. Minnesota was admitted as the 32nd U.S. state on May 11, 1858, created from the eastern half of the Minnesota Territory. The state has a large number of lakes, and is known by the slogan "Land of 10,000 Lakes". Its official motto is "L'Étoile du Nord" (French: "Star of the North"). Minnesota is the 12th largest in area and the 21st most populous of the U.S. states; nearly 60 percent of its residents live in the MinneapolisSaint Paul metropolitan area (known as the "Twin Cities"), the center of transportation, business, industry, education, and government and home to an internationally known arts community. The remainder of the state consists of western prairies now given over to intensive agriculture; deciduous forests in the southeast, now partially cleared, farmed and settled; and the less populated North Woods, used for mining, forestry, and recreation. Minnesota is known for its progressive political orientation and its high rate of civic participation and voter turnout. Until European settlement, Minnesota was inhabited by the Dakota and Ojibwe/Anishinaabe. During the 19th and early 20th centuries, the large majority of the European settlers emigrated from Scandinavia and Germany, and the state remains a center of Scandinavian American and German American culture. In recent decades, immigration from Asia, the Horn of Africa, and Latin America has broadened its historic demographic and cultural composition. Minnesota's standard of living index is among the highest in the United States, and the state is also among the best-educated and wealthiest in the nation.  - The Appalachian Mountains, often called the Appalachians, are a system of mountains in eastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. It once reached elevations similar to those of the Alps and the Rocky Mountains before naturally occurring erosion. The Appalachian chain is a barrier to east-west travel, as it forms a series of alternating ridgelines and valleys oriented in opposition to most roads running east or west.  - Missouri (see pronunciations) is a state in the Midwestern region of the United States, achieving statehood in 1821. With over six million residents, it is the eighteenth most populous state and host to the mean center of United States population. The largest urban areas are St. Louis, Kansas City, Springfield, and Columbia. The capitol is in Jefferson City on the Missouri River. The state is the twenty-first most extensive by area and is geographically diverse. The Northern Plains were once covered by glaciers, then tallgrass prairie, and now the deep soils yield great agricultural productivity. In the South are the Ozarks, a forested highland, providing timber, minerals, and recreation. The Mississippi River forms the eastern border of the state, eventually flowing into the swampy Missouri Bootheel.  - The Missouri River is the longest river in North America. Rising in the Rocky Mountains of western Montana, the Missouri flows east and south for before entering the Mississippi River north of St. Louis, Missouri. The river takes drainage from a sparsely populated, semi-arid watershed of more than half a million square miles (1,300,000 km), which includes parts of ten U.S. states and two Canadian provinces. When combined with the lower Mississippi River, it forms the world's fourth longest river system.    After reading the paragraphs above, we are interested in knowing the entity with which 'st. francis river' exhibits the relationship of 'continent'. Find the answer from the choices below.  Choices: - africa  - asia  - north america
Answer:
north america