How do you calculate degree of freedom for chi square

Ascientist and her team counted 200 individual deer in an area of 10 square kilometers. what is the population density?

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

Anton created a chart listing different types of materials. which best complete the chart?