The Cycle of Change Mode

The Cycle of Change Model
It is recognized that the following is a challenging exercise, because it requires that you make a very difficult choice; however, this exercise will also ensure that you have fully evaluated each step of the Cycle of Change Model, and that you have considered the requisite value of each step to the overall organizational change and transformation process.
If you were required to choose only one step in the Cycle of Change Model as being most important to the success of any major organizational change or organizational transformation initiative, which step would you choose? Why?