Correct Answer: Agitated

Solution : The most appropriate choice is the fourth option.

Explanation : We have to look for an antonym that contrasts with the calm and tranquil state associated with the word serene. Agitated is the suitable choice as it represents a state of nervousness, restlessness, or disturbance, which is the opposite of the serene and peaceful state.

The meanings of the other options are as follows:

• Unperturbed : This adjective means undisturbed or not troubled.
• Pleased : This adjective means satisfied or happy.
• Composed : This adjective means calm and collected.

Therefore, the correct antonym is agitated .