Ab welchem Alter darf man in Deutschland an der Wahl zum Deutschen Bundestag teilnehmen?

Why this is the correct answer

German citizens gain the right to vote in federal elections (Bundestagswahlen) at the age of 18, which is also the age of legal adulthood. Voting at 16 is allowed in some state and local elections but not at the federal level, and 21 or 23 are not thresholds used in the German electoral system.