Question: Amtrak's headquarters provides service to which two rail lines in Virginia?

Context paragraphs:
Millcreek (UTA station): Millcreek is a light rail station in South Salt Lake, Utah, United States serviced by the Blue Line and the Red Line of Utah Transit Authority's TRAX light rail system and by UTA's 3500 South MAX bus rapid transit line.  The Blue Line provides service from Downtown Salt Lake City to Draper.  The Red Line provides service from the University of Utah to the Daybreak Community of South Jordan.  The 3500 South MAX provides service from this station to Magna via West Valley City.

Keystone Corridor: The Keystone Corridor is a 349-mile (562 km) railroad corridor between Philadelphia and Pittsburgh, Pennsylvania, that consists of two rail lines: Amtrak's Philadelphia-to-Harrisburg main line, which also hosts SEPTA's Paoli/Thorndale Line commuter rail service; and the Norfolk Southern Pittsburgh Line.  The corridor was originally the Main Line of the Pennsylvania Railroad.

Washington Union Station: Washington Union Station is a major train station, transportation hub, and leisure destination in Washington, D.C. Opened in 1907, it is Amtrak's headquarters and the railroad's second-busiest station with annual ridership of just under 5 million.  The station also serves MARC and VRE commuter rail services, the Washington Metro subway, intercity bus lines, and local Metrobus buses.

Transportation in Greater Los Angeles: The transportation system of Greater Los Angeles includes 7 commuter rail lines, amtrak service, a subway system within the city of Los Angeles, and numerous highways.  Los Angeles is integrated into the Interstate Highway System by Interstate 5, Interstate 10, and Interstate 15, along with numerous auxiliary highways and state routes.  Bus service is also included locally within the area by numerous local government agencies.  Subways and light commuter rail lines are present within Los Angeles proper, allowing mass transportation within the city.  Commuter railroads are run by Metrolink.  AMTRAK has numerous railroad lines that connect Los Angeles to the rest of the country.

Courthouse (UTA station): Courthouse is a light rail station in Downtown Salt Lake City, Utah, United States serviced by all three lines of Utah Transit Authority's TRAX light rail system.  The Blue Line provides service from Downtown Salt Lake City to Draper.  The Red Line provides service from the University of Utah to the Daybreak Community of South Jordan.  The Green Line provides service from the Salt Lake City International Airport to West Valley City (via Downtown Salt Lake City).

Virginia Railway Express: The Virginia Railway Express (VRE) (reporting mark VREX) is a regional/commuter rail service that connects the Northern Virginia suburbs to Union Station in Washington, D.C., via two lines: the Fredericksburg Line from Fredericksburg, Virginia, and the Manassas Line from Broad Run/Airport station in Bristow, Virginia.

TRAX (light rail): As of 2013 TRAX has three lines in service.  The Blue Line provides service from Downtown Salt Lake City to Draper.  The Red Line provides service from the University of Utah to the Daybreak Community of South Jordan.  The Green Line provides service from Salt Lake City International Airport to West Valley City.

Ballpark (UTA station): Ballpark is a light rail station in the People's Freeway neighborhood of Salt Lake City, Utah, in the United States, served by all three lines of Utah Transit Authority's TRAX light rail system.  The Blue Line provides service from Downtown Salt Lake City to Draper.  The Red Line provides service from the University of Utah to the Daybreak Community of South Jordan.  The Green Line provides service from the Salt Lake City International Airport to West Valley City (via Downtown Salt Lake City).

900 South (UTA station): 900 South is a light rail station in Downtown Salt Lake City, Utah, in the United States, served by all three lines of Utah Transit Authority's TRAX light rail system.  The Blue Line provides service from Downtown Salt Lake City to Draper.  The Red Line provides service from the University of Utah to the Daybreak Community of South Jordan.  The Green Line provides service from the Salt Lake City International Airport to West Valley City (via Downtown Salt Lake City).  The station opened on 19 September 2005 and is operated by the Utah Transit Authority.  900 South is notable for being the first infill station constructed along an existing line of the TRAX system.

Main Line (Pennsylvania Railroad): The Main Line of the Pennsylvania Railroad was a rail line in the U.S. state of Pennsylvania, connecting Philadelphia with Pittsburgh via Harrisburg.  The rail line was split into two rail lines and now all of its right of way is now a cross-state corridor, composed of Amtrak's Philadelphia to Harrisburg Main Line (includes SEPTA's Paoli/Thorndale Line service) and the Norfolk Southern Railway's Pittsburgh Line.

Supporting paragraphs: Virginia Railway Express Washington Union Station
Answer: the Fredericksburg Line from Fredericksburg, Virginia, and the Manassas Line