The correct answer is Cumulative flow diagram.

A Cumulative flow diagram is a stacked area chart that shows how many work items were in each workflow state over time. The diagram makes it easy to see the size of each state and how work flows through the process over a two week period or any other timeframe.

Burndown chart is incorrect because a burndown chart tracks remaining work over time for a sprint or iteration and it does not show the count of items in each workflow state.

Velocity chart is incorrect because velocity shows how much work a team completes per sprint and it does not break work down by workflow state over time.

Control chart is incorrect because a control chart highlights cycle time or lead time variation for individual items and it does not display stacked counts of items in each state across a time range.

Sprint report is incorrect because a sprint report summarizes committed versus completed work for a sprint and it does not provide a continuous, state by state view of work items across a two week period.

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