increase in available ecological niches increase of atmospheric oxygen to present levels increase in genetic diversity among surviving organisms increase in interbreeding between organisms of different species
I gave my students this multiple choice question: Which was a main force driving extensive speciation when the environment became hospitable to life after the Permian mass extinction?

Only one answer is correct among these 4 choices:
- increase in available ecological niches
- increase of atmospheric oxygen to present levels
- increase in genetic diversity among surviving organisms
- increase in interbreeding between organisms of different species

Could you tell me which one is correct?

increase in available ecological niches