Final answer:
Involuntary absenteeism occurs when an individual misses work due to unforeseen or uncontrollable circumstances, such as illness.
Step-by-step explanation:
Involuntary absenteeism refers to situations when employees are absent from work for reasons beyond their control. Out of the options provided, missing work due to illness is an example of involuntary absenteeism since the individual does not choose to be sick and is unable to attend work as a result. In contrast, taking a planned vacation, attending a scheduled training session, and choosing to work remotely are all voluntary and typically planned or agreed-upon in advance with the employer.