The correct answer is C) he forced Jews to wear yellow star badges.
One way that Hitler ensured discrimination against Jewish people was that he forced Jews to wear yellow star badges.
The Nazi forced Jewish people to wear the yellow start badge to discriminate them. Germany has just invaded Poland in 1939 when Hitler approved the use of the yellow star to identify Jews. This allowed the Nazi to identify them quickly, capture them and sent them to the camps. This was humiliating for the Jews.
The other options of the question were a) he forced Jews to become German citizens and b) he forced Jews to leave Germany.