How should ecologists study moon jelly population at Glacier Sea?

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

The third stage of cellular respiration is (2 points)

What are the student's observations and inferences before he starts his investigation?