Given the question: Information:  - The Nordic countries or Nordics are a geographical and cultural region in Northern Europe and the North Atlantic, where they are most commonly known as Norden (lit., "The North"). They consist of Denmark, Finland, Iceland, Norway, and Sweden, including their associated territories (Greenland, the Faroe Islands, and the Åland Islands).  - Mälaren, historically referred to as Lake Malar in English, is the third-largest freshwater lake in Sweden (after Vänern and Vättern). Its area is 1,140 km² and its greatest depth is 64 m. Mälaren spans 120 kilometers from east to west. The lake drains, from south-west to north-east, into the Baltic Sea through the Södertälje Canal, Hammarbyslussen, Karl Johansslussen and Norrström. The easternmost bay of Mälaren, in central Stockholm, is called Riddarfjärden. The lake is located in Svealand and bounded by the provinces of Uppland, Södermanland, Närke, and Västmanland. The two largest islands in Mälaren are Selaön (91 km²) and Svartsjölandet (79 km²).  - During the 6th millennium BC, agriculture spread from the Balkans to Italy and Eastern Europe, and also from Mesopotamia to Egypt. World population was essentially stable at numbers ranging between approximately 5 and 7 million.  - Stockholm County ("Stockholms län") is a county or "län" (in Swedish) on the Baltic sea coast of Sweden. It borders Uppsala County and Södermanland County. It also borders Mälaren and the Baltic Sea. The city of Stockholm is the capital of Sweden. Stockholm County is divided by the historic provinces of Uppland (Roslagen) and Södermanland (Södertörn). More than one fifth of the Swedish population lives in the county. Stockholm County is also one of the statistical "riksområden" (national areas) according to , Nomenclature of Territorial Units for Statistics within the EU. With more than two million inhabitants, Stockholm is the most densely populated county of Sweden.  - The Stone Age was a broad prehistoric period during which stone was widely used to make implements with an edge, a point, or a percussion surface. The period lasted roughly 3.4 million years, and ended between 8700 BCE and 2000 BCE with the advent of metalworking.  - Sweden, officially the Kingdom of Sweden (Swedish: ), is a Scandinavian country in Northern Europe. It borders Norway to the west and Finland to the east, and is connected to Denmark in the southwest by a bridge-tunnel across the Öresund. At , Sweden is the third-largest country in the European Union by area, with a total population of 10.0 million. Sweden consequently has a low population density of , with the highest concentration in the southern half of the country. Approximately 85% of the population lives in urban areas.  - Stockholm City Centre ("Stockholms innerstad", "Innerstaden", "Inre staden") is the city centre of Stockholm in Sweden. The entire city of Stockholm is also the centre of the Stockholm Metropolitan Area.  - T-Centralen (Swedish for "The T-Central"; T being an abbreviation for "tunnelbana", the Swedish word for "underground" or "subway") is a metro station that forms the heart of the Stockholm metro system, in the sense that it is the only station where all three of the system's lines meet. That, its central location, and its connections with other modes of transport make it the most used metro station in Stockholm. The station is located in the Norrmalm borough of Stockholm, between Sergels torg (Sergel's Square) and the street of Vasagatan.  - The Baltic Sea (  ; ) is a sea of the Atlantic Ocean, enclosed by Scandinavia, Finland, the Baltic countries, and the North European Plain. It includes the Gulf of Bothnia, the Bay of Bothnia, the Gulf of Finland, the Gulf of Riga, and the Bay of Gdask. The sea stretches from 53°N to 66°N latitude and from 10°E to 30°E longitude. A mediterranean sea of the Atlantic, with limited water exchange between the two bodies, the Baltic Sea drains through the Danish islands into the Kattegat by way of the straits of Øresund, the Great Belt, and the Little Belt.  - An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. A grouping of geographically or geologically related islands is called an archipelago, e.g. the Philippines.  - The Stockholm archipelago is the largest archipelago in Sweden, and the second-largest archipelago in the Baltic Sea (the largest being across the Baltic in Finland).  - Biography. Early life. It is known that Birger grew up and spent his adolescence in Bjälbo, Östergötland but the exact date of his birth remains uncertain and available historical sources are contradictory. Examinations of his mortal remains indicate that he was probably about 50 upon his death in 1266 which would indicate a birth around 1216. However, his father Magnus Minnesköld is assumed to have died no later than 1210, which would lead to an assumed birth a few years earlier. Under any circumstance, he was the son of Ingrid Ylva, who according to Olaus Petri was a daughter of Sune Sik and granddaughter of King Sverker I of Sweden, which would make Birger a matrilineal member of the House of Sverker. His brothers or half-brothers  Eskil, Karl, and Bengt  were all born long before 1200, and it can therefore be assumed that they had another mother. He was also a nephew of the jarl Birger Brosa from the House of Bjelbo. The combination of this background proved to be of vital importance.  - The Stockholm metro (literally: "Stockholm's Tunnel Rail") is a metro system in Stockholm, Sweden. The first line opened in 1950, and today the system has 100 stations in use, of which 47 are underground and 53 above ground. There are three coloured main lines on the tube maps. These do however form seven actual routes (with different termini). Routes number 17, 18 and 19 (belonging to the green main line), 13 and 14 (red main line) and 10 and 11 (blue main line) all go through Stockholm City Centre in a very centralized metro system. All seven actual lines use The "T-Centralen" hub station. Apart from this Central Station for the metro, there exists just one other junction, the "Fridhemsplan" station, although both the green and red lines are mutually accessible at the "Slussen" and "Gamla Stan" stations.  - Husby is a station on the blue line of the Stockholm metro , located in the district of Husby , northern Stockholm . The station was inaugurated on 5 June 1977 . The distance to Kungsträdgården is 15 km.  - Stockholm (or ) is the capital of Sweden and the most populous city in the Nordic countries; 932,917 people live in the municipality, approximately 1.5 million in the urban area, and 2.3 million in the metropolitan area. The city is spread across 14 islands on the coast in the southeast of Sweden at the mouth of Lake Mälaren, by the Stockholm archipelago and the Baltic Sea. The area has been settled since the Stone Age, in the 6th millennium BC, and was founded as a city in 1252 by a Swedish statesman Birger Jarl. It is also the capital of Stockholm County.    What is the relationship between 'husby metro station' and 'metro station'?
The answer is:
instance of