Part a: which statement identifies the central idea of the text? in death marches in the holocaust

a
few prisoners were subjected to death marches, as allied troops were able to intervene during the evacuations.
b
while treacherous, the ss never intended to kill any prisoners during the evacuation marches as they were needed for labor.
c
towards the end of the war, some concentration camp prisoners were able to escape the ss during evacuations.
d
“death marches” ended up becoming a tool for nazi murder, but that was not the original intention of the evacuations.