The air stays cleaner. Cars can travel at faster speeds. The skills of the drivers improve. It becomes safer to drive on the roads.
I gave my students this multiple choice question: Cities control the amount of pollution that is allowed to come from cars. How does this most likely help people?

Only one answer is correct among these 4 choices:
- The air stays cleaner.
- Cars can travel at faster speeds.
- The skills of the drivers improve.
- It becomes safer to drive on the roads.

Could you tell me which one is correct?

The air stays cleaner.