Plz help I will mark you brainlist plz I don't know what to do

What did not occur in the proterozoic eon a)the oxygen levels increase greatly in the atmosphere,b)the emergence of the eukarya , c)muti cella’s eukaryotic organisms began to diversify,d)anaerobic bacteria kept thriving with more oxygen

In which layer do organisms on earth love?

As a result of these processes the single celled organism accomplishes