The correct answer is A. Milestone
Step-by-step explanation:
In a timeline, events are organized according to time. This tool can be used as part of projects to organize each of the events or stages that are part of a project. Moreover, in a timeline, there are milestones or important achievements.
For example, if the project is to build a house, one of the milestones or important achievements is to complete the plane of the building. This implies each of the milestones helps to check the progress of the project. After all, if all the milestones are achieved the project will be completed.