The correct option is Cycle Time.

Cycle Time measures the elapsed time to complete a work item after it transitions to the active or in progress state. It captures the duration from when work actually starts until it is finished which matches the question about the time to complete work items after they become active.

Velocity is a throughput metric that shows how much work a team completes in an iteration and it is usually expressed in story points or completed items so it does not represent elapsed time for individual work items.

Lead Time measures the total time from when a request or ticket is created until it is delivered and it therefore includes waiting time before work starts which makes it broader than the metric asked for in the question.

Burndown Chart visualizes remaining work over time for a sprint or release and it tracks progress rather than showing the elapsed time for individual items after they move to an active state.

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