Explanation:

- Ecstasy: This word refers to a state of overwhelming joy or happiness. It's an intense feeling of delight or bliss.

- Option 1, Mourning: This means expressing deep sorrow, especially for someone who has died. It's unrelated to happiness or joy, and therefore not a synonym for ecstasy.

- Option 2, Bliss: This is a state of perfect happiness or joy. It's a direct synonym for ecstasy as both words describe a similar intense feeling of happiness.

- Option 3, Fantasy: This refers to imagining things, often unrealistic or improbable, and does not relate to the emotional state described by ecstasy.

- Option 4, Appreciation: This is about recognizing the value or worth of something, which while positive, does not capture the intense joy implied by ecstasy.