How can changes in human activities reduce air pollution?

Do you have choices or? if not: if humans stop using cars, buses, and other things that run on fossil fuel we would stop releasing so much carbon dioxide into our atmosphere. of course there are natural emissions that release carbon dioxide into our atmosphere but 87% of carbon dioxide releases com from the burning of fossil fuel. If humans start using energy efficient thing then it would improve the amount of carbon dioxide released immediately. 

B. would complete your answer. give me brainliest!

The correct answer is a. we know this because n (hap) + n (hap) = 2n (dip).