Final answer:
The execution of a project's activities starts in the project's performance phase, which involves transitioning from planning to implementation, and is critical for the successful completion of the project.
Step-by-step explanation:
The execution of the project's constituent activities begins in the project's performance phase. Once the preparatory phase is complete and the detailed design is in place, this phase signifies the transition from planning to actual implementation. As described in the phases of the project, this performance phase involves activities such as creating drawings, building models, and constructing scenery for the production. Flexibility and adaptability are critical during this phase, as changes may need to be made to address unforeseen challenges and ensure successful project completion.
Documenting and communicating the results is also a crucial aspect of the performance phase, as it ensures that clients or customers are aware of the project's progress. Moreover, obtaining buy-in from all stakeholders is essential for the project's smooth execution and must be reaffirmed throughout the project lifecycle, including during the performance phase.