Question

Which activity would contribute the most to water pollution?

Using too much fertilizer

Desertification caused by natural climate change

Deforestation caused by natural forces

Reforestation

Answer 1

i think the choices was for air pollution

Answer 2

Albeit this is not a Mathematics question, I will try to answer.
The last one should not be true, since you are 'helping' the environment by reforesting regions that were devastated by human forces. B and C are caused by natural agents, so the Nature wouldn't pollute itself, that doesn't make a lot of sense. All that's left is the first one :-)