Answer:
D. Falling action
Step-by-step explanation:
If you look at a plot diagram viewed in chronological order, it begins with an exposition (the beginning). Then, conflict occurs, which leads to the rising action (the middle, or the major part of the story). It reaches the climax, where the MC experiences their critical problem in the story. Finally, the story gradually dies down with the falling action (the end) to the resolution (conclusion).
The falling action occurs after the climax which leads to the resolution (conclusion or end) of the story. It is not the rising action nor the conflict because they occur before the climax (see below). The resolution is the outcome of the story, therefore cannot be before the conclusion.
Exposition - Conflict - Rising action - Climax - Falling action - Resolution
(Beginning) (Middle) (Conclusion)