They use fuels which pollute the environment very badly.

它们使用严重污染环境的燃料。

Most cars use fuels which pollute the environment very badly.

大多数汽车使用严重污染环境的燃料。

fuel (up) a car

给车加油

Research suggests warm colors fuel our appetites.

研究表明暖色会刺激我们的食欲。