Explanation:

- The word "Ebullient" describes someone who is full of energy, excitement, and enthusiasm. It conveys a sense of overflowing happiness or being lively.

- Option 1: Carefree - This word suggests a lack of worries or concerns. While it conveys a relaxed attitude, it doesn't directly contrast with the full of life and excitement of "ebullient."

- Option 2: Dejected - This word means feeling sad and disheartened. It conveys a state of low spirits, which is the opposite of being lively and enthusiastic.

- Option 3: Buoyant - This is similar to ebullient, as it means cheerful and optimistic. It is not an antonym.

- Option 4: Roguish - This describes someone who is playful in a mischievous way. It doesn’t directly oppose being ebullient.

- Answer: Dejected is indeed the most appropriate antonym of ebullient.