What must you do to activate a customer journey after creating it?

To activate a customer journey in Dynamics 365 Marketing, the process involves ensuring that the journey is fully configured and free of errors before making it active for execution. The correct option indicates that you need to check for errors first to ensure there are no issues that could affect the customer journey's performance. Once you confirm that there are no errors, you can proceed to activate the journey by going live, making it ready for the intended audience.

The activation process is crucial because it ensures the integrity of the customer journey. If there are issues present, customers may not have the experience intended, leading to underperformance of the marketing initiative. Therefore, checking for errors ensures all elements are functioning correctly before the journey is live.

While other options mention validation or publishing, they do not emphasize the need for error checking or the specific step of going live, which is critical for the overall success of the customer journey. Thus, checking for errors followed by going live is the proper sequence to ensure a successful activation.