Outlook defines a(n) ____ as an activity that occurs at least once and lasts 24 hours or longer.

A) item
B) task
C) event
D) occurrence

An event is described as an activity that occurs at least once and lasts for 24 hours or longer. This distinguishes it from a task or item, which may be shorter and can be completed within a shorter timeframe. An occurrence is a more general term that does not necessarily imply a specific duration or frequency.