In what ways did the Nazis kill their victims?

First, victims should remain totally unaware that they are about to die. Second, perpetrators need not touch, see, or hear their victims as they die. Third, the death blow should avoid leaving any visual indications of harm on the victims’ bodies. And finally, the death blow should be instantaneous.

Explanation:

answer; i believe its called ; checks   and balances;

answer; membership group;