the emissions from volcanic activity the level of pollution caused by people the amount of ozone in the stratosphere the amount of oxygen produced by trees
I gave my students this multiple choice question: The U.S. Environmental Protection Agency (EPA) was established in 1970 to address problems that existed in the environment. Which is the EPA most likely interested in reducing?

Only one answer is correct among these 4 choices:
- the emissions from volcanic activity
- the level of pollution caused by people
- the amount of ozone in the stratosphere
- the amount of oxygen produced by trees

Could you tell me which one is correct?

the level of pollution caused by people