The term probability of detection BEST describes the:

Probability of detection refers to the likelihood that an intrusion or unauthorized action will be identified by the security system. It is a key performance metric used to evaluate the effectiveness of electronic security components such as sensors and alarms. A high probability of detection means a more reliable system.

A (System validation) is a phase where detection may be measured, but it’s not the definition.

B (Officer response) is unrelated to detection probability.

D (Response timing) is part of delay or intervention, not detection.