Wie wird die Verfassung der Bundesrepublik Deutschland genannt?

Why this is the correct answer

Germany's constitution is formally titled the Grundgesetz, adopted on May 23, 1949, by the Parliamentary Council in Bonn. Its official English translation renders Grundgesetz as Basic Law or Constitution. It was originally conceived as a provisional document pending reunification, but after 1990 it became the permanent constitution of a unified Germany.