recycling paper products watering the lawn once a week designing cars that are fuel efficient using coal to generate electricity
I gave my students this multiple choice question: Which of these reduces the need for people to use nonrenewable resources?

Only one answer is correct among these 4 choices:
- recycling paper products
- watering the lawn once a week
- designing cars that are fuel efficient
- using coal to generate electricity

Could you tell me which one is correct?

designing cars that are fuel efficient