Which of the following is an example of an achievement?

The correct answer is completing a challenging project, as it represents a specific goal that has been attained through effort, skill, and commitment. Achievements are typically understood as the successful realization of goals or tasks that require significant effort, persistence, and capability. Completing a project, especially when it is described as challenging, demonstrates not only that the individual has set a target but also that they have navigated obstacles and applied their abilities to reach a successful conclusion.

The other choices, while related to productive activities, do not encapsulate the same sense of accomplishment. Planning systematically suggests preparation and organization but does not indicate the completion of a specific goal. Studying continuously implies ongoing effort and dedication but lacks a definitive outcome to signify achievement. Participating in discussions is a valuable activity that can enhance learning and collaboration, yet it does not denote the successful completion of a task. Thus, completing a challenging project stands out as a clear example of an achievement.