turning down the volume on the television using biodegradable materials using public transportation instead of driving recycling paper
I gave my students this multiple choice question: Which of these daily activities can most directly help reduce air pollution in a city?

Only one answer is correct among these 4 choices:
- turning down the volume on the television
- using biodegradable materials
- using public transportation instead of driving
- recycling paper

Could you tell me which one is correct?

using public transportation instead of driving