Which of the following is the BEST definition of an Incident?

Describing a loss of ability to operate to specification more closely aligns with the ITIL definition of a Failure rather than the formal definition of an Incident.

A change of state with significance for the management of a Configuration Item describes an Event in ITIL terminology, not an Incident.

A warning that a threshold has been reached or a failure has occurred describes an Alert, which may trigger Incident management but is not itself an Incident.

The formal ITIL definition states that an Incident is 'an unplanned interruption to an IT service or reduction in the quality of an IT service,' covering both complete outages and degraded service states. This definition is intentionally user-impact-centric and distinguishes Incidents from planned changes, making the unplanned and service-affecting nature the defining characteristics.