forest fires in mountain regions succession that transforms grassland to forest decomposition of a desert rodent flash flooding in a country area
I gave my students this multiple choice question: A student prepares a report on gradual environmental changes. Which is the best topic for this report?

Only one answer is correct among these 4 choices:
- forest fires in mountain regions
- succession that transforms grassland to forest
- decomposition of a desert rodent
- flash flooding in a country area

Could you tell me which one is correct?

succession that transforms grassland to forest