Why were people forced to go on "death marches"?

SS authorities did not want prisoners to fall into enemy hands alive to tell their stories to Allied and Soviet liberators.

The SS thought they needed prisoners to maintain production of armaments wherever possible.

Some SS leaders, including Himmler, believed irrationally that they could use Jewish concentration camp prisoners as hostages to bargain for a separate peace in the west that would guarantee the survival of the Nazi regime.

- the right to vote -

im not sure if its a or b but i think its b because of the past tense