Explanation:

- The given word is "Obvious," which means something clear or readily apparent.

- Hidden: Means something is not visible or easily found, making it the opposite of obvious.

- Plain: Indicates something that is simple or clear, which is somewhat similar to obvious.

- Vapid: Refers to something dull or lacking in spirit but not directly opposed to obvious.

- Active: Suggests being engaged or lively but doesn't directly counter obvious.

Hidden aligns as the opposite because it implies something not immediately seen or understood, contrasting with obvious.

Answer: Hidden (Option 2)

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