For part four you will again need to do what ever you need to do. So if your in

For part four you will again need to do what ever you need to do.
So if your intervention B phase was effective in part two, you should have finished your first reversal (second A phase) this week so you will simply re-apply your original intervention again for the final week. You will need to discuss any unexpected changes in behavior during the final week of data collection and why you think that happened.
However, if your initial intervention was not effective during part two (the B phase), and you introduced a new or modified intervention during week three (C Phase), you will then re-evaluate if your C phase was effective or not to determine what you would need to do for Part four. If the C phase was not effective you will nee to again modify your intervention and begin the D Phase using this new contingency during part four. However, if the behavior appeared to change as a function of the intervention during the C phase, you would then move into the first reversal (return to the baseline condition) and begin the A phase for your final week.
Regardless of the scenario that applies to this behavioral intervention you should provide a brief discussion of why you think the overall projected worked or not and if it was not effective what could you do differently to get better performance in the future.
Make sure you include a copy of your graph with all four weeks of data labeled appropriately.