Final answer:
Groceries represent a variable expense in Tiffany's budget because the cost can change each month, unlike fixed expenses such as a car loan payment or rent.
Step-by-step explanation:
Tiffany's variable expenses are costs that can fluctuate from month to month. Among the options given, groceries is a variable expense because the amount she spends can vary widely based on her choices, sales, season, and other factors. In contrast, a car loan payment, insurance payment, rent, and savings contributions are typically fixed expenses with consistent amounts due each period.