The correct options are:
- Improved engines; engines were improved significantly so that they can have the same power and agility but by using less fuel.
- Cleaner burning fuels; it has been invested a lot of time and money into improving the fuels and making them as effective as possible but also removing or lowering the most dangerous components towards the environment.
- Catalytic converters; this devices for exhaust emission control manage to convert the toxic gasses and polutants into less toxic pollutants by managing to catalyze a redox reaction.
