a decrease in the thickness of soil a decrease in the amount of erosion an increase in the bacterium population an increase in the production of oxygen
I gave my students this multiple choice question: Forest fires occur in many areas due to drought conditions. If the drought conditions continue for a long period of time, which might cause the repopulation of trees to be threatened?

Only one answer is correct among these 4 choices:
- a decrease in the thickness of soil
- a decrease in the amount of erosion
- an increase in the bacterium population
- an increase in the production of oxygen

Could you tell me which one is correct?

a decrease in the thickness of soil