How did rivers affect the interaction between prehistoric groups?

a. they protected groups from invasion.
b. they invited interaction with other regions.
c. they kept groups separate most of the time.
d. they let groups divide and form unique cultures.

The Holocaust, also known as the Shoah, was the genocide of European Jews during World War II. Between 1941 and 1945, Nazi Germany and its collaborators systematically murdered some six million Jews across German-occupied Europe, around two-thirds of Europe's Jewish population.

Explanation:

Germany implemented the persecution in stages. Following Adolf Hitler's appointment as Chancellor on 30 January 1933, the regime built a network of concentration camps in Germany for political opponents and those deemed "undesirable", starting with Dachau on 22 March 1933.[6] After the passing of the Enabling Act on 24 March,[7] which gave Hitler plenary powers, the government began isolating Jews from civil society; this included boycotting Jewish businesses in April 1933 and enacting the Nuremberg Laws in September 1935. On 9–10 November 1938, eight months after Germany annexed Austria, Jewish businesses and other buildings were ransacked or set on fire throughout Germany and Austria on what became known as Kristallnacht (the "Night of Broken Glass"). After Germany invaded Poland in September 1939, triggering World War II, the regime set up ghettos to segregate Jews. Eventually thousands of camps and other detention sites were established across German-occupied Europe.