Explanation:

- Jovial: This word describes someone who is cheerful and full of good humor.

- Option 1: Mirthful

- Means showing happiness or joyous spirit.

- Synonymous with jovial rather than an antonym.

- Option 2: Cool-headed

- Describes someone calm and composed, often in stressful situations.

- It is not directly related to being jovial or gloomy.

- Option 3: Convivial

- Means friendly, lively, and enjoyable.

- Similar to being jovial, not an antonym.

- Option 4: Gloomy

- Means dark, depressing, or lacking in cheer.

- This is the opposite of jovial.

- Correct Answer:

- Option 4: Gloomy