What is the German constitution called?

EDITORIAL LEARNING AID

Why is this answer correct?

The Basic Law of 1949 is the constitution of the Federal Republic of Germany. "Volksgesetz", "Bundesgesetz" and "Deutsches Gesetz" are not names for the constitution; a federal statute is merely a single law.

The constitution is called the Basic Law — since 1949.

This translation and explanation are editorial learning aids. The official German wording and answer key govern the examination.