The correct answer is so Jews could be easily identified, so Jews could be persecuted, and so Jews could be arrested more easily.
Hitler passed a law requiring Jewish people to wear a yellow star so Jews could be easily identified, so Jews could be persecuted, and so Jews could be arrested more easily.
Hitler and the Nazis passed a law on September 1, 1941, implementing the yellow star identification for Jewish people. That was a measure to identify in public the Jewish people and causing them humiliation and isolation. The Jews had to wear a yellow Star of David in their clothes while in public places.
