Final answer:
Sandra's National Guard unit being deployed to Iraq makes her an involuntary short-term traveler.
Step-by-step explanation:
In the given scenario, Sandra's National Guard unit is being deployed to Iraq for four months. Based on the options provided, she would fall under the category of an involuntary short-term traveler. As a member of the National Guard, Sandra's deployment is mandatory, and although it is for a relatively short duration, she does not have the choice to decline the assignment.