Question: Metrovías operates a transit metro system that first opened in which year ?
Sentence (from "Buenos Aires Underground"): The Buenos Aires Underground (Spanish: "Subterráneo de Buenos Aires" ), locally known as Subte (] , from "subterráneo" – 'underground' or 'subterranean'), is a mass transit metro system that serves the area of the city of Buenos Aires, Argentina.
Relevant evidence: No