The correct answer is The extent to which safeguards lower risk to an acceptable level.

The extent to which safeguards lower risk to an acceptable level captures the idea that control effectiveness is judged by how much risk is reduced and whether the remaining risk is within the organization\'s tolerance. Effectiveness is demonstrated by measurable reductions in likelihood or impact and by evidence from testing, monitoring, and audits.

The degree to which controls have been applied across the environment is incorrect because coverage or deployment does not guarantee that controls actually reduce risk. A control can be widely applied and still be ineffective if it is misconfigured or unsuitable.

Security Command Center is incorrect because it is the name of a product or tool and not a definition of what control effectiveness means. Tools can assist with measurement and management but they do not define the concept.

The capacity to stop every security incident from happening is incorrect because absolute prevention is unrealistic. Control effectiveness is about reducing and managing risk to an acceptable level rather than eliminating all incidents.

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