Answer:
Step-by-step explanation:
The exothermic reaction between iron and oxygen that produces rust can generate heat, which can be utilized to create portable hand-warmers. By using a chemical reaction that produces rust, heat can be released, which can then be harnessed and packaged into a small, portable device that can be used to warm hands during cold weather. This is a common application of the exothermic reaction between iron and oxygen, and can be found in many commercially available hand-warmers.
The other options listed in the question are not relevant to the exothermic reaction between iron and oxygen that produces rust. Creating rusty fenders for a car is not a desirable outcome, as it would result in unsightly and potentially damaging rust on the car's exterior. Creating cooling headbands is not related to the exothermic reaction between iron and oxygen that produces rust. Creating non-rusting machines is also not related to this reaction, as the reaction specifically produces rust as a byproduct.