The correct answer is C. Hardworking.
Diligence is the quality of being careful, persistent, and thorough. It is often associated with hard work and dedication. People who are diligent are often successful in their endeavors because they are willing to put in the time and effort necessary to achieve their goals.
A fool is a person who is foolish or stupid. They may be easily deceived or tricked, and they may not be able to think clearly or make good decisions.
An unhappy person is someone who is not satisfied with their life. They may be feeling sad, angry, or frustrated.
A disappointment is something that fails to meet expectations. It can be a person, event, or situation that does not turn out the way you wanted it to.
In conclusion, the correct answer to the question “DILIGENT : A. Fool B. Unhappy C. Hardworking D. Disappointment” is C. Hardworking.