Answer: B - Learning from Experience is an ongoing principle.
Key takeaway: When the project is started and the Lessons Log created, the principle of Learning from Experience is applied by documenting lessons from previous similar projects. When the project is closed down, lessons learned within the project are documented for reference in future projects. As the project progresses, it is important to learn from experience on a continual basis, both for reference for future projects and for the continued development of the current project.