PLEAS HELP How do you know that the letter from Harry Truman is a primary source?

A. It was written to members of Truman's immediate family.

B. It was written by Truman himself about current events.

C. It contains information about earlier events.

D. It contains facts about Truman's life.

Which statements describe einsatzgruppen? check all that apply. they were considered the last step in the "final solution." they were part of the german army. they carried out mass executions. they were known as mobilized killing units. they were used by germany during the invasions of poland and the soviet union.