The correct answer is Epic burndown report.

The Epic burndown report is built to show remaining work for an epic over time and it displays scope changes and completed work across multiple sprints so it is the report you would use to forecast how many more sprints are required to finish an epic that has been active for several months.

Cumulative flow diagram shows the amount of work in each workflow state over time to help identify bottlenecks and stability issues and it does not directly present remaining epic scope or a sprint based forecast.

Burndown chart typically tracks remaining work for a single sprint or a fixed release window and it is not focused on the multi sprint progress and scope changes of an epic that spans many sprints.

Control chart displays cycle time and the distribution of issue lead times to help assess process predictability and it is not intended to forecast the number of sprints left for an epic.

Velocity chart reports the average completed work per sprint and it can support rough forecasting but it does not show remaining epic scope or scope changes over time in the way the epic burndown report does so it is not the best single chart for this question.

Full AWS Practitioner Certification Question