Final answer:
The IDEAL Model is an organizational improvement model composed of five phases that guide systematic change and development efforts within organizations.
Step-by-step explanation:
The organizational improvement model that is based on five phases: initiating, diagnosing, establishing, acting, and learning is known as the D) IDEAL Model. This model provides a structured framework for organizations to follow in order to implement changes that lead to improvement and development. The IDEAL Model aligns with the descriptions provided, as each phase correlates with a step in the improvement process: Initiating involves identifying the need for change, Diagnosing encompasses analyzing the current situation, Establishing involves planning and setting goals, Acting includes the implementation of the plan, and Learning is about reflecting on the results and adapting as necessary.