plants and animals invading an abandoned crop field mangroves stabilizing the soils on tropical coasts minerals spurring rapid plant growth lichen growth on rocks
I gave my students this multiple choice question: Which is an example of primary ecological succession?

Only one answer is correct among these 4 choices:
- plants and animals invading an abandoned crop field
- mangroves stabilizing the soils on tropical coasts
- minerals spurring rapid plant growth
- lichen growth on rocks

Could you tell me which one is correct?

lichen growth on rocks