Final answer:
The antonyms for activism, agent, and unknown are apathy, principle, and known respectively.
Step-by-step explanation:
The antonym for activism is apathy. Apathy refers to a lack of interest or concern, while activism involves actively working towards a cause or promoting change. For example, someone who is apathetic towards the environment would not engage in any environmental activism. The antonym for agent is principle. While an agent represents or acts on behalf of someone else, a principle refers to a fundamental truth or guideline. For instance, in a school, the principal is the guiding principle, not an agent of the students or teachers. The antonym for unknown is known. When something is unknown, it is not familiar or recognized. Conversely, when something is known, it is familiar and recognized. For example, in a mystery novel, the identity of the unknown criminal becomes known at the end of the story.