find new coal resources in the earth clean up the litter in neighborhoods clean up the water pollution in local lakes walk or ride a bike instead of driving a car
I gave my students this multiple choice question: What is one way to help slow down or stop the greenhouse effect?

Only one answer is correct among these 4 choices:
- find new coal resources in the earth
- clean up the litter in neighborhoods
- clean up the water pollution in local lakes
- walk or ride a bike instead of driving a car

Could you tell me which one is correct?

walk or ride a bike instead of driving a car