Q: Why did people stop adding lead to gasoline?


Read this paragraph and choose the correct option from the provided answers:

Gasoline and oils are complex chemical mixtures designed to burn in a way that will efficiently produce energy while emitting a minimal amount of air pollution. The refining of gasoline has improved engine performance but is much more complicated than simply using the crude products extracted from oil wells, as was common in the late 1800s. Most gasoline contained lead at one time, because this additive helped the engine run more smoothly. However, this caused lead contamination in the environment, so new “unleaded” formulations were created that could be burned smoothly without the addition of poisonous heavy metals. Oils for lubrication have special additives that reduce engine wear. Some special fuel blends have also been created to generate more power in race car engines.

 Choices:

- bad smell

- to expensive

- explosions

- environmental pollution


A:
environmental pollution