Which of the following best describes an assignment that has been completed by the officer?

The phrase "Assignment Complete" serves as a clear and straightforward way to communicate that a specific task or responsibility has been carried out to its conclusion. It encapsulates the idea that the officer has finished the work that was designated to them, and it is a commonly understood term within law enforcement contexts.

The other options, while they may imply completion, do not carry the same clarity or formality associated with reporting the completion of an assignment. "Observation Finished" suggests that a specific monitoring task is done, but it doesn’t encompass the broader scope of an assignment that may include various tasks. "Mission Accomplished" sounds more informal and may not accurately reflect police reporting standards. Similarly, "Duty Concluded" could imply that the officer's entire shift or responsibility has ended, rather than focusing on the completion of a specific assignment. Hence, "Assignment Complete" is the most precise and appropriate terminology for indicating that an assigned task has been successfully finished.