Information:  - Stuttgart ( Swabian: "Schduagert"), often nicknamed the ""Schwabenmetropole"" in reference to its location in the center of Swabia and the local dialect spoken by some natives, is the capital and largest city of the German state of Baden-Württemberg. It is located on the Neckar river in a fertile valley locally known as the "Stuttgarter Kessel" an hour from the Swabian Jura and the Black Forest. Stuttgart's name comes from the Old High German word ""Stuogarten"," or "stud farm"  a reference to the city's founding in 950 AD as a stud farm. Stuttgarts urban area has a population of 623,738, and a further making it the sixth largest city in Germany, 2.7 million people live in the citys administrative region, and another 5.3 million people in its metropolitan area, making it the fourth largest metropolitan area in Germany.  - Schleswig-Holstein is the northernmost of the 16 states of Germany, comprising most of the historical duchy of Holstein and the southern part of the former Duchy of Schleswig. Its capital city is Kiel; other notable cities are Lübeck and Flensburg.  - Düsseldorf (Low Franconian, Ripuarian: "Düsseldörp" ) is the capital city of the German state of North Rhine-Westphalia and the seventh most populous city in Germany. Düsseldorf is an international business and financial centre, renowned for its fashion and trade fairs. The city is headquarters to one Fortune Global 500 and two DAX companies. Messe Düsseldorf organises nearly one fifth of premier trade shows.  - Wardersee is a lake in Kreis Segeberg , Schleswig - Holstein , Germany . At its elevation , its surface area is 3.6 km² .  - Cologne is the largest city in the German federal State of North Rhine-Westphalia and the fourth-largest city in Germany (after Berlin, Hamburg, and Munich). It is located within the Rhine-Ruhr metropolitan region, one of the major European metropolitan regions and the largest in Germany, with more than ten million inhabitants.  - Frankfurt am Main is a metropolis and the largest city in the German state of Hesse and the fifth-largest city in Germany, with a 2015 population of 731,095 within its administrative boundaries, and 2.3 million in its urban area. The city is at the centre of the larger Frankfurt Rhine-Main Metropolitan Region, which has a population of 5.8 million and is Germany's second-largest metropolitan region after Rhine-Ruhr. Since the enlargement of the European Union in 2013, the geographic centre of the EU is about to the east of Frankfurt's CBD, the Bankenviertel. Frankfurt is culturally and ethnically diverse, with around half of the population, and a majority of young people, having a migration background. A quarter of the population are foreign nationals, including many expatriates.  - Lübeck is a city in Schleswig-Holstein, northern Germany, and one of the major ports of Germany. On the river Trave, it was the leading city of the Hanseatic League, and because of its extensive Brick Gothic architecture is listed by UNESCO as a World Heritage Site. In 2015, it had a population of 218,523.  - Berlin is the capital and the largest city of Germany as well as one of its constituent 16 states. With a population of approximately 3.5 million people, Berlin is the second most populous city proper and the seventh most populous urban area in the European Union. Located in northeastern Germany on the banks of rivers Spree and Havel, it is the centre of the Berlin-Brandenburg Metropolitan Region, which has about 6 million residents from more than 180 nations. Due to its location in the European Plain, Berlin is influenced by a temperate seasonal climate. Around one-third of the city's area is composed of forests, parks, gardens, rivers and lakes.  - Germany, officially the Federal Republic of Germany, is a federal parliamentary republic in central-western Europe. It includes 16 constituent states, covers an area of , and has a largely temperate seasonal climate. With about 82 million inhabitants, Germany is the most populous member state of the European Union. After the United States, it is the second most popular immigration destination in the world. Germany's capital and largest metropolis is Berlin. Other major cities include Hamburg, Munich, Cologne, Frankfurt, Stuttgart and Düsseldorf.    After reading the paragraphs above, we are interested in knowing the entity with which 'wardersee' exhibits the relationship of 'lake outflow'. Find the answer from the choices below.  Choices: - havel  - neckar  - rhine  - spree  - trave
Answer:
trave