A burndown chart is a graphical tool that shows the amount of work remaining versus time. It is often used to track the progress of a Sprint or a release. The work remaining is usually measured in terms of effort, such as hours or story points, and it is plotted on the vertical axis. The time is measured in terms of days or weeks, and it is plotted on the horizontal axis. The burndown chart starts with the total amount of work at the beginning of the Sprint or release, and it ideally ends with zero work at the end. The slope of the burndown chart indicates the rate of progress, or the velocity, of the Scrum Team12.
The other options are not what burndown charts track. Accumulated cost, accumulated business value, and individual worker productivity are not relevant or useful metrics for Scrum Teams, as they do not reflect the value or the quality of the product. Scrum Teamsfocus on delivering potentially releasable increments of the product that meet the Definition of Done, and they use empirical feedback to inspect and adapt their work13. References: 1: Understanding and Applying the Scrum Framework 2: Burndown Chart 3: Managing Products with Agility