The word "dehumanizing" can be understood by breaking it down into its roots and affixes. The prefix "de-" often indicates removal or reversal, and the root "human" relates to human qualities or characteristics. The suffix "-izing" generally indicates a process or action.
Putting this together, "dehumanizing" suggests the process of removing or taking away a person's humanity or human qualities.
Given this analysis, the best choice from the options provided is:
taking a person’s humanity away.