Final answer:
The word that most nearly means 'radical' is 'Extreme'. Words like 'Conventional', 'Traditional', and 'Conservative' imply resistance to change, whereas 'radical' suggests a far-reaching, revolutionary approach.
Step-by-step explanation:
The word that most nearly means radical is Extreme (Option A). The term 'radical' is often used to describe actions, ideas, or approaches that are very different from traditional or usual methods, typically to the point of being far-reaching or revolutionary. Unlike 'radical', the words 'Conventional' (Option B), 'Traditional' (Option C), and 'Conservative' (Option D) generally pertain to established practices, beliefs, or attitudes that resist change and tend to preserve existing conditions or restore traditional ones, which are opposite to the essence of 'radical'. Therefore, 'Extreme' is the word that most closely aligns with the concept of 'radical', indicating a position or action that is at the far end of a spectrum and not typical or moderate.