Implementation activities primarily encompass which of the following?

Implementation activities are crucial steps taken to put a project plan into action. They focus on the actual execution of project tasks, which include defining the major activities required to achieve the project goals, outlining the responsibilities of team members, and acknowledging any constraints that may affect the project's progress.

Choosing activities, responsibilities, and project constraints is essential because these elements guide how the project is coordinated and executed. Major activities ensure that all necessary tasks are identified and scheduled effectively, while assigning responsibilities clarifies who will handle each task. Recognizing constraints helps to anticipate potential challenges and prepare strategies to mitigate them.

In contrast, elements like upper management strategies, product development timelines, and sales and marketing initiatives may influence a project's context or direction but do not directly address the core of implementation. Implementation is fundamentally about managing the project's execution efficiently, making option C the most suitable choice.