Nitrogen.
Nitrogen and oxygen = Air
nitrogen
Nitrogen
You can get your bike tires pumped at a bike shop, a gas station with an air pump, or by using a portable bike pump at home.
It's nitrogen.
Air is used to inflated car tyres but cars can be equipped with nitrogeon inflated tyres but this is usually only beneficial to race cars
Keep tires pumped up. Tires that are underinflated have a higher rolling resistance on the road.
Nitrogen
It is nitrogen.
I think it is Nitrogen. The normal air mixture pumped into regular road cars is not efficient at high speeds and will lose pressure easily. If that happens there could be catastrophic consequence at high speed. That is why they use nitrogen If you pump nitrogen into the tires of your regular road car, you need not check tire pressure for 3 months.
Nitrogen, because it is an inert gas.
The best tires for a small car would be the ones that the car manufacturer recommends you use on the car. If you keep good tires on your car and check them every now and then you will get better gas mileage.