Question: On which long U-shaped line of the Washington Metro transit system is Grosvenor-Strathmore station?

Context paragraphs:
Grosvenor–Strathmore station: Grosvenor–Strathmore (formerly Grosvenor, pronounced /ˈɡroʊvnər/) is a rapid transit station on the Red Line of the Washington Metro in North Bethesda, Maryland.  The first above-ground station on the Red Line heading northwest from Washington, D.C., it is one of a number of stations on the Rockville Pike corridor in Montgomery County.

Washington Metro: The Washington Metro, known colloquially as Metro and branded Metrorail, is the heavy rail rapid transit system serving the Washington metropolitan area in the United States.  It is administered by the Washington Metropolitan Area Transit Authority (WMATA), which also operates Metrobus service under the Metro name.  Besides the District of Columbia, Metro serves several jurisdictions in the states of Maryland and Virginia.  In Maryland, Metro provides service to Montgomery and Prince George's counties; in Virginia, to Arlington and Fairfax counties and the independent city of Alexandria.  Combined with its ridership in the independent Virginia cities of Falls Church and Fairfax, the Metro service area is largely coextensive with the inner ring of the Washington metropolitan area.  The system is currently being expanded to reach Dulles International Airport and Loudoun County, Virginia.  It operates mostly as a subway in the District itself, while most of the suburban tracks are at surface level or elevated.

Metro (Minnesota): Metro (styled as METRO) is a light rail and bus rapid transit system which serves the Minneapolis-St.  Paul metropolitan area.  As of 2016, the system consists of three lines (Blue, Green and Red) connecting Downtown Minneapolis and St. Paul with Bloomington and Minneapolis-St.  Paul International Airport, with several extensions in planning stages.  The system is operated by Metro Transit for the Blue and Green, and by the Minnesota Valley Transit Authority for the Red Line.

Red Line (Washington Metro): The Red Line of the Washington Metro rail rapid transit system serves 27 stations in Montgomery County, Maryland and the District of Columbia in the United States.  It is a primary line through downtown Washington and the oldest and busiest line in the system.  It forms a long, narrow "U", capped by its terminal stations at Shady Grove and Glenmont.

Rapid transit in Canada: There are three heavy rail and three light rail rapid transit systems operating in Canada.  The Toronto subway was the first rapid transit system in Canada when it opened a 12-station line in 1954.  It has since grown to encompass three heavy rail lines and one intermediate rail line and has the most number of stations of any system in Canada with 69.  Construction has begun on the Eglinton Crosstown Line and the Toronto-York Spadina Subway Extension, which will add 28 new stations and a total of 27.6 km of new track.  Montreal introduced the Montreal Metro in 1966 and has now become the most popular rapid transit system in the country with 1,263,800 daily riders.  The Vancouver SkyTrain, an automated guided line, was opened in January 1986 for the Expo 86 world fair and is the longest rapid transit system in Canada with a system length of 79.6 km .  There are three light rail systems operating in Canada including systems in Calgary (the CTrain), Edmonton (the Edmonton LRT), and Ottawa (the O-train).  There is one light rail system under construction in Kitchener-Waterloo named Ion rapid transit.

Metro Transit rolling stock: The opening of the METRO Blue Line in 2004 marked the beginning of Metro Transit's expansion into rail transit, 50 years after the last Twin Cities Rapid Transit streetcars were taken out of service.  Several new rail transit projects are either under construction or in planning stages and more are expected to be explored in the near future.  Metro Transit will likely be acquiring a significant amount of rolling stock as these new projects move forward.

Metro Transit (Minnesota): Metro Transit is the primary public transportation operator in the Minneapolis–Saint Paul area of the U.S. state of Minnesota and the largest operator in the state.  The system is a division of the Metropolitan Council, the region’s metropolitan planning organization (MPO), averaging 267,700 riders each weekday, carrying 90% to 95% of the transit riders in the region on a combined network of regular-route buses, light rail and commuter rail.  The remainder of transit ridership is generally split among suburban “opt-out” carriers operating out of cities that have chosen not to participate in the Metro Transit network.  The biggest opt-out providers are Minnesota Valley Transit Authority (MVTA), Maple Grove Transit and Southwest Transit (SW Transit).  The University of Minnesota also operates a campus shuttle system of its own, which ranks second in the state, measured by ridership.

List of Washington Metro stations: The Washington Metro (commonly called Metro, and branded Metrorail) is a rapid transit system serving Washington, D.C. and neighboring communities in Maryland and Virginia, both inside and outside the Capital Beltway.  With an average weekday ridership of 748,000, the Washington Metro is the third-busiest rapid transit system in the United States, behind the Chicago "L" and the New York City Subway.  s of 2015 , the system has 91 active stations spread out on six lines with 117 mi of tracks.  An infill station at Potomac Yard is planned to open in 2020 on the Yellow and Blue lines, and six more stations are planned in 2020 as part of the Phase II of the Silver Line.

MetroLink (St. Louis): MetroLink (reporting mark BSDA) is the light rail transit system in the Greater St. Louis area of Missouri and the Metro East area of Illinois.  The system consists of two lines (Red Line and Blue Line) connecting Lambert-St.  Louis International Airport and Shrewsbury, Missouri with Scott Air Force Base near Shiloh, Illinois through downtown St. Louis.  The system features 37 stations and carries an average of 53,123 people each weekday.  As of the first quarter of 2015, it is second only to Minneapolis Metro Transit's Blue and Green lines in the Midwestern United States in terms of ridership, and is the 11th-largest light rail system in the country.

Madison County Transit: Madison County Transit, or MCT for short, is a bus and bike trail transportation system that serves the citizens of Madison County, which is located in Illinois approximately 20 mi northeast of St. Louis.  It was created in 1980 by the Madison County Board to improve transportation in Madison County, and is a completely separate transit system from the St. Louis Metro Transit system which includes MetroLink, which doesn't operate into Madison County, though the buses connect with many MetroBus routes and even serve MetroLink stations in East St. Louis, Belleville and Downtown St. Louis.

Supporting paragraphs: Grosvenor–Strathmore station Red Line (Washington Metro)
Answer: Red Line