Answer:
-fuel cost
-groceries
Step-by-step explanation:
Variable expense: Amount of money paid on this expense changes every month
Non-discretionary: This is an expense that you cannot get by without
In today's world, you need fuel for your car in order to travel to your job and other places, therefore it is non-discretionary. The amount you spend on fuel changes every month because you do not travel the same exact distance every month, so it is also a variable expense.
You need groceries to live, therefore it is non-discretionary. The amount you spend on groceries changes every month as well, so it is also a variable expense.
You can eliminate the other options because:
Car loan payment = fixed expense (not non-discretionary)
Gym membership = fixed expense and also discretionary (you can live without it)
Insurance premium = fixed expense
Vacation cost = discretionary