Context : Futebol Clube do Porto, MHIH, OM (Portuguese pronunciation: (futɨˈβɔɫ ˈkluβ(ɨ) ðu ˈpoɾtu)), commonly known as FC Porto or simply Porto, is a Portuguese sports club based in Porto, which is best known for the professional football team playing in the Primeira Liga, the top flight of Portuguese football. 
Question : What football league is FC Porto a part of?
Primeira Liga