An event is best described as any change of state that has significance for the management of a service, so option C is correct. In ITIL, events are not automatically negative. They may indicate normal operations, warnings, thresholds being crossed, or conditions that require attention. Event management helps organizations observe and respond appropriately to what is happening in live systems. A user request is a service request, not an event. A sudden damaging occurrence may be an incident or disaster, depending on context. The addition or removal of something affecting services relates more to a change or configuration item context. By defining events broadly as significant state changes, ITIL enables organizations to monitor services proactively and respond before issues become major service interruptions.