Explanation:

- Obstinate means stubborn or unwilling to change one's opinion or action.

- Option 1: Self-evident means obvious or clear without needing proof.

- Option 2: Palpable means something that can be felt or perceived, almost tangible.

- Option 3: Hidden means concealed or not visible.

- Option 4: Unmistakable means very clear or obvious.

- Correct Answer: Option 3, Hidden

Hidden stands as the closest antonym because it suggests a lack of obviousness, contrasting with obstinate's clear and unwavering stance.