by reducing the amount of pollution by increasing the number of car sales by increasing the amount of carbon dioxide in the air by eliminating the possibility of accidents
I gave my students this multiple choice question: In what way do transit systems, such as buses, benefit society?

Only one answer is correct among these 4 choices:
- by reducing the amount of pollution
- by increasing the number of car sales
- by increasing the amount of carbon dioxide in the air
- by eliminating the possibility of accidents

Could you tell me which one is correct?

by reducing the amount of pollution