Respuesta :
The headquarters for both major parties are located in "Washington DC," since this area is in fact the main political location of a variety of different political entities.
The correct answer is Washington D.C., since both the Republican Party and the Democratic Party have their headquarters in the District of Columbia.
The Republican headquarter is located in 310 First Street SE, Washington DC; while the Democratic one is located in 430 South Capitol St. SE, of the same city.