mixing of pollutants with rain erosion of topsoil by clearcutting runoff of fertilizer used in farming thinning of the atmospheric ozone layer
I gave my students this multiple choice question: Some plant species are more tolerant of acidic soil than others. The tolerant species are favored in areas affected by which consequence of human activity?

Only one answer is correct among these 4 choices:
- mixing of pollutants with rain
- erosion of topsoil by clearcutting
- runoff of fertilizer used in farming
- thinning of the atmospheric ozone layer

Could you tell me which one is correct?

mixing of pollutants with rain