The correct answer is D. agitated.
A serene mind is one that is calm and peaceful. It is not easily disturbed or upset. A person with a serene mind is able to think clearly and rationally, even in difficult or stressful situations.
A person who is agitated is restless and upset. They may be easily angered or frustrated. They may also have difficulty concentrating or thinking clearly.
A person who is agitated is not likely to be the pioneer of a great revolution. A revolution requires careful planning and execution. It also requires the ability to think clearly and rationally, even in the face of opposition. A person who is agitated is not likely to be able to do these things.
The other options are not correct because they do not describe a person who is agitated.
A person who is nervous is anxious or worried. They may be easily startled or frightened. They may also have difficulty concentrating or thinking clearly.
A person who is jocular is humorous or playful. They may be quick to make jokes or laugh. They may also be easily amused.
A person who is earnest is sincere and honest. They are often serious and hardworking. They may also be very dedicated to their beliefs or goals.