The prefix de- means not and opposite of. The prefix de- also means

Merriam-Webster's Eleventh Collegiate Dictionary (2003) lists several words in which the prefix un- negates a word that de- has previously negated:

Such instances are quite rare, however, in comparison to the number of words that use re- to override a de- negation. Thus, for example, if a doctor decontaminates a wound with antiseptic, but bacteria later reappear, we say that the new germs "recontaminate" the wound, not that they "undecontaminate" it.

answer; i believe the answer is (b) fascism;