Which of the following statements is true?

Allied forces bombed railroad lines to slow the transport of Jews to concentration camps.
Allied leaders believed Nazi ghettoes and camps kept civilians out of the worst of the war’s violence.
Allied nations encouraged open Jewish immigration as soon as they learned of the Holocaust.
Allied powers knew about Nazi death camps but focused their efforts on the defeat of Germany.

Allied powers knew about Nazi death camps but focused their efforts on the defeat of Germany.

The statement that is true is: Allied powers knew about Nazi death camps but focused their efforts on the defeat of Germany.