Explanation:

- Fatuous means silly or foolish, often lacking intelligence or thought.

- Option 1: Foolish

- This is a synonym of fatuous. Both words imply a lack of wisdom or thought.

- Option 2: Illusory

- This means deceptive or not real. It's unrelated to the meaning of fatuous.

- Option 3: Terrible

- This implies something is very bad or dreadful. It does not relate to being foolish or silly.

- Option 4: Real

- This means actual or true, grounded in reality. It is the opposite of illusions or fantasies.

- Correct Antonym: Option 1: Foolish