Final answer:
The step that must occur at the end of the systems implementation phase and not concurrently with others is the post-implementation review. The correct option is D.
Step-by-step explanation:
The question pertains to the systems implementation phase of a project. Within this phase, certain steps can happen at the same time, while others need to occur sequentially. The step that could not occur concurrently with other steps and would occur at the end is D. Post-implementation review.
This is because the post-implementation review is a retrospective look at the overall performance and effectiveness of the system after it has been fully implemented and is in use. It evaluates if the system meets the set objectives and identifies any areas for improvement for future projects.
While steps like employee training, data conversion, and software programming can occur alongside each other as part of the implementation process, the review can only happen after these steps have been completed to assess their success. The correct option is D.