Q: You are presented with the quiz "What has a positive effect on an ecosystem?"   But you don't know the answer, so you turn to your teacher to ask for hints. He says that "planting trees has a positive impact on an ecosystem" and "destruction of Trees is taking place, pollution of air is the Result of cutting trees with pace".   So, what's the best answer to the question?

Pick your answer from: [i] maintaining air pollution; [ii] removing habitats; [iii] stopping air pollution; [iv] to stay warm; [v] in the frog family; [vi] Electric generators; [vii] increasing air pollution; [viii] genetic diversity;
The answer is:
[iii]