Should a single person without children list no dependents?

Presuming you don't have something like an elderly grandmuother or brother or such you support ...meaning contribute more than 50% of the cost of their upkeep to, YES. I conquer, if you don't have dependents, then you should not claim one unless you have another sibling,family member living with you at least 6 months and where you pay at least 50% of their upkeep