Historically, most cars have run on gasoline (汽油), but that may change in the future: cars can also run on other liquid fuels (液体燃料) and electricity.
Gasoline is from oil. The energy in gasoline comes from hydrocarbons (碳氢化合物) Gasoline provides great power for cars. However, it causes environmental problems, like air pollution and temperature rise. So gasoline can't be the best fuel.
Another choice is electricity. Electricity cars can be as efficient (效能好的) as cars using gasoline, And they produce less pollution. But electric cars themselves are more expensive. Good news is that the cost has been lower and there are more and more places for the cars to get electricity ever since 2010.
The other choices are other liquid fuels. Many of these can be stored in the same places as gasoline, and used in the same cars. They can also be friendly to the environment.
One way to make such fuels is to get CO2 from the air and put it in water. Through chemical reaction, hydrocarbons can be created. However, these fuels take up more space.
Another way is to make such fuels from plants which take in carbon from the air. These fuels are greener in use. But not all of them can be as efficient as gasoline.
For a fuel to be the best, people have to be able to afford it. Unluckily, almost every green technology is more expensive than that of using gasoline. Governments and car producers are doing everything they can to cut down the costs. In the end, the best fuel will be both affordable for car users and green for our planet.
