The einsatzgruppen did what during the invasion of the soviet union?

Einsatzgruppen ( operative groups)  were a part of the feared Schutztaffel (SS)  . They killed many civilians, Jews and Soviet Communist Party Commissars. Reportedly they took part in mass shootings from the early stage of the Soviet Union invasion. As a terror tactic against local population they also used public hangings.

the answer for 3 is b and the answer for 4 is d

the answer is a, salt plain