Of the 1.1 to 1.5 million people killed at auschwitz, the largest group was made of

The largest group that was killed at Auschwitz are people with Jewish backgrounds and ethnicity. While there are other ethnicity's there, the Jewish group was the largest group, and were either put into Birkenau (the work concentration camp next to Auschwitz), or sent directly to Auschwitz (a death camp, where they gas prisoners in large numbers and burned).

~

The correct answer is option D