Due to a tight project schedule, a project manager did not document lessons learned throughout the project cycle. However, at the end of the project, he finally documented the lessons learned. Your comment on this is:

This is not OK. Lessons learned must be documented throughout the project as well as at the end of the project.

This is OK. Lessons learned should be documented at the end of the project.

This is not OK. Lessons learned need to be documented throughout the project and must not be done at the project’s end.

This is correct. Lessons learned are intended to be documented only at the project’s end.