what did it mean to be chosen

THis means being chosen by the guards to be put to death.

There is a kind of sick play on words with the word chosen because they Jews have always called themselves God's chosen people. The Nazi's in their sick way undermine the beauty of that religious belief by using it as the ultimate control over the Jewish people in the camps. Processed doesn't have any implied threat in the word, and any words that actually stated what was going to happen would be appalling -- to both the Jews and the Nazi's. It is kind of ironic that the Nazi's didn't seem to have any problem doing what they were doing, but they didn't want to talk about it in the harsh words of reality; it is as if they are hiding from it for themselves too.