Which of the following is not part of an instructional system?

The correct choice is Program Diagnosis, as it is typically not considered a core part of an instructional system. In the context of an instructional system, the focus is primarily on the stages that facilitate the design, delivery, and evaluation of educational programs.

Program Evaluation involves assessing the effectiveness of a training program, ensuring that the objectives are met and that learners are achieving the desired outcomes. Program Delivery refers to the method and process of imparting knowledge to learners, which could include various teaching methods and learning environments. Program Design encompasses the planning and structuring of the educational content, including curriculum development and instructional methods.

In contrast, while diagnosis might play a role in identifying learner needs or gaps in knowledge, it is not a formal component of the instructional system itself. Instead, it serves more as a preliminary step that can influence elements like delivery and design but does not fit into the defined cycles of the instructional system.