Original sentence: It was at its height in Central and Eastern Europe, which had more than seven million Jews in 1939.The mass killings were systematically conducted in virtually all areas of Nazi-occupied territory in what are now 35 separate European countries
Edited sentence: It was at its worst in Central and Eastern Europe, which had more than seven million Jews in 1939.The slaughter was systematically conducted in virtually all areas of Nazi-occupied territory in what are now 35 separate European countries